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Dealing With Interruptions

September 2, 2015 by Fiction Editor Beth Hill
last modified September 15, 2015

To give our sentences variety and complexity, we include much more than the basic information in every sentence. We include digressions and asides, commentary, parentheticals, and other interrupters.

Our sentences are rich in meaning and full of a wide range of word groupings. Some of those groupings interrupt the main thrust of the sentence. And of those interrupters, some we want to highlight while others we want to de-emphasize.

Interrupters can provide character or narrator commentary, additional information, or even emphasis.

Interrupters can be appositives, adjectives, adverbs, names, participial phrases, absolute phrases, prepositional phrases, interjections, and commentary.

Interrupters actually interrupt the meaning and flow of sentences and must be set off with the appropriate punctuation so readers can make sense of the information contained within the interrupter as well as within the sentence as a whole.

Writers have three choices of punctuation to set off sentence interrupters—commas, parentheses, and em dashes.

When interrupters fall midsentence, always use a pair of punctuation marks to surround them. And be careful to not mix different punctuation marks. For example, don’t use a dash to begin the interrupter and a comma to end it.

The scarlet silk—the soft and beautiful square of it, was torn. X

The scarlet silk—the soft and beautiful square of it—was torn.



You’ll use pairs of commas for digressions or supplementary information much more often in fiction than you’ll use dashes or parentheses. Commas aren’t your only choice, obviously, but their use is far more common than the other two choices.

Commas allow the text to flow. They help make sections of text manageable without drawing too much attention to themselves. They also don’t draw extra attention to the text between them. Instead, the text is neutral, blending into the sentence. Comma pairs aren’t intended either as a means of accenting text or downplaying it. They do make sections of text easier for the reader to group together and to understand.

Pairs of commas can surround single words, phrases, and clauses. Interrupters of many types can be nestled within commas.

“The truth, Daniel, is that you shouldn’t have followed me here.”

Nedra, hoping to score at least sixteen points in the first half, had practiced the night before the game until her arms trembled.

The bride, serene and smiling, sauntered down the aisle.

The button, the blue one, was broken.

He ran, surprisingly, toward the growling grizzly.


Parentheses (in BrE, round brackets)

Parentheses are quite noticeable. While the text between them is downplayed, the punctuation itself stands out. For this reason, many recommend that there’s no place for parentheses in fiction.

I won’t go that far—plenty of writers use parentheses in first-person narration for snarky thoughts or humorous asides—but I will suggest you limit their use. Parentheses are actually unnecessary in first-person narration because every thought is the thought of the viewpoint character/narrator. You don’t need to set thoughts aside, as if the character is speaking out of the side of her mouth to the reader. Everything the character says is overheard by the reader.

You would, however, use such asides as a style choice to show that the narrator/viewpoint character is aware that he’s speaking to the reader or an audience.

A problem with parentheses is that they can seem too much like author intrusion, as if the author is filling the reader in with a wink and a nod. As if the author is pulling back the curtain and whispering from the wings.

Parentheses, because the punctuation marks themselves stand out, can also point to the mechanics behind the fiction, to the setup. And anything that distracts from the fictional world, pointing back to the 3-D world, can prevent the reader from getting lost in the fictional characters and their adventures.

Parentheses are necessary and quite useful for nonfiction. But for fiction, you may want to rethink or restrict them.

Exceptions, of course, if you want to imply that your narrator/viewpoint character is speaking directly to the reader. That’s rare these days, but not unheard of.

Unlike commas, parentheses can be used to enclose full sentences or even paragraphs. Information is de-emphasized when it’s enclosed between parentheses. It can be pulled out completely and never be missed because it truly is something other, something additional to the main thrust of the sentence.

~  A sentence containing text set apart by parentheses must be grammatical without the parenthetical element.

~  Punctuation interrupted by the information between the parentheses comes after the closing parenthesis.

~  Parentheses are always used in pairs.

My aunt Eleanor (a mean woman who had nonetheless shared her home with me) is currently traveling through South America. [No comma after me because there is no comma in the sentence without the interrupter.]

Lucy Mallory, the wildly famous pinup girl from the forties (and a friend of my mother’s), would be visiting in a week. [A comma is required after mother’s because it would be required without the interruption.]

The new receptionist was gorgeous (and a guy!); the CEO’s new assistant was brainy, snooty, and taller than Mr. Crandall; and the chairman of the board was shrewd, mixing up the executive floor the way she had.

The steak (rare) was ready, the corn (raw) was overbuttered, and the French fries (the cheapest brand available) were still frozen.

The success (as well as the failures) were the fault of the sales department. X

The success (as well as the failures) was the fault of the sales department.

~  Parentheses don’t have to fall midsentence; they can come at the end.

My brother is planning to get married on my birthday (the last day of June). [Note the period is outside the parentheses.]

~  If a full sentence is enclosed in parentheses, the period goes inside.

Our school’s JV team won all their meets. (The varsity squad lost all of theirs.) And the parents threw them an ice cream blowout.

The third sentence in the previous example refers to the JV team. Anything relating to the varsity squad must be included inside the parentheses. Or you could rewrite to give the varsity squad equal attention.

Our school’s JV team won all their meets. The varsity squad, however, lost all their meets. The parents of the JV kids threw them an ice cream blowout to celebrate.


Em dashes (in BrE, em rule)

Dashes highlight or emphasize interrupters. If you want information to stand out, if you want to draw attention to it, use dashes.

If the phrase or clause you’re setting apart already contains a comma, using dashes to set it apart from the rest of the sentence will help reduce reader confusion.

As with sentences with parentheses, the sentence interrupted by dashes must make grammatical sense without the information contained between the dashes. That is, if you removed the dashes and everything between them, the sentence must still make sense.

Alfie needed to eat his breakfast—cook, eat, and clean up—in less than fifteen minutes.

Sally liked me to read her fairy tales—she loved those featuring handsome princes—before going to sleep.

Sally liked me to read her fairy tales—she loved those featuring handsome princes—so I always included Prince Phillip. X

The previous example doesn’t make sense. The final section of text does not complete the beginning of the sentence; it instead takes into account the interrupter.

Better would be—

Sally liked me to read her fairy tales. She loved those featuring handsome princes, so I always included Prince Phillip.

~  If the interrupter already contains commas, use dashes rather than more commas.

The littlest child—cuddly, cute, and sweet, sweet, sweet—was passed from adult to adult over the course of the hike.

~  While you could use multiple sets of dashes in the same sentence, rewriting is often the better choice. As always, you don’t want the reader noticing your punctuation.

Alfred Tennyson—the gardener, not the poet—showed up twice a week—always five minutes early—without fail.

~  When a digression, aside, or comment comes at the end of a sentence, you can still set it off with a dash. Yet there is no closing dash.

My dog came running when I called—and I had to chase her down when she raced straight through the house and out the front door.

~  When dashes are used, omit punctuation such as commas. The dash replaces the comma.

After reaching for the nails—and knocking them over the edge of the roof—I let Hildy do the hammering.

After reaching for the nails and knocking them over the edge of the roof, I let Hildy do the hammering.

After reaching for the nails (and knocking them over the edge of the roof), I let Hildy do the hammering.

After reaching for the nails—and knocking them over the edge of the roof—, I let Hildy do the hammering. X



AmE uses no spaces between the em dash and the letters before and after it. BrE typically includes space at both ends (and if you include this space, use an en dash rather than an em dash), yet it does allow for the dash to bump up against the letters as an option. (Apparently the Oxford folks use the em dash without spaces.)


Interrupters between commas, parentheses, and dashes are not capitalized (unless they are proper names). A full sentence enclosed by parentheses does begin with a capital letter.

Parentheses are always used in pairs. Dashes are used in pairs midsentence, but you can end a sentence with a digression set off with a single dash. What you don’t want to do is mix one dash with one comma. If you need two punctuation marks, use two of the same mark.

Teddy—lost in the woods—grew sleepy and hungry.

Teddy, lost in the woods—grew sleepy and hungry. X

Teddy—lost in the woods, grew sleepy and hungry. X

The punctuation for interruptions, asides, and commentary need to be introduced at logical breaks in the sentence.

I need my medicine—my migraines can be horrible, my credit cards—and of course my passport. X

I need my medicine—my migraines can be horrible—my credit cards, and of course my passport.


Use commas most of the time, especially if you don’t need to draw extra attention to the interrupter or don’t need to play it down.

Use parentheses sparingly in fiction. The information within the parentheses is de-emphasized and might not have a place in the sentence anyway. Use parentheses when you want to downplay the information between them but also want to let readers know you’ve got something to tell them. Use parentheses when you want to make readers aware of the narrator, viewpoint character, or author speaking to them.

Use dashes when you want to accentuate the information between the dashes, drawing special attention to the material, maybe giving it a distinctive flourish. Also use dashes rather than commas when the interrupter or aside or comment already contains commas.

Use dashes rather than commas when a comma splice would be created without the dashes.

Sally liked me to read her fairy tales, she loved those featuring handsome princes, before going to sleep. X

Sally liked me to read her fairy tales—she loved those featuring handsome princes—before going to sleep.

Use a dash to set off material that otherwise might be separated from the sentence by a colon or a period.

I needed him—it was a yin-yang thing.

I needed him: it was a yin-yang thing.

I needed him. It was a yin-yang thing.


You’ve got options for punctuating interruptions, yet one choice will likely be better in one situation while another choice fits a different situation better.

Explore the use of the em dash—give your sentences a new feel and create a variety of sentence formats and rhythms. On the other hand, don’t overuse dashes. Readers shouldn’t find dashes in every other sentence.

Reduce the use of parentheses in your fiction if you use them often. Unless you’re trying to wink at the reader, sharing inside jokes and letting the reader know that you know he is there, consider not using them at all.

If you’ve got specific questions about when to use commas, parentheses, and dashes, ask in the comments.



Tags: , ,     Posted in: Grammar & Punctuation

30 Responses to “Dealing With Interruptions”

  1. Pat Garcia says:

    Hi Beth,
    I am glad that I joined your site because everything that you have published so far helps me. Especially this lecture on interrupters, it is very helpful. So. what is an en dash? I know what em dashes are, but the en expression lost me.

    And I have a question that doesn’t pertain to the article. When writing thoughts of a character can I use italics?


    • Patricia, an en dash is shorter than an em dash and longer than a hyphen. They’re used when we indicate a range of years, such as 1992–1998. We also use them in place of a hyphen when we write something like pre–Civil War artifacts.

      To create an en dash in Windows, type ALT0150. That’s holding the ALT key down while you type 0150 on your numeric keypad. To create an em dash, type ALT0151.

      I’ve included the hyphen, en dash, and em dash so you can see the difference in their lengths.


      You can use italics for character thoughts, but you may not want to. Check out this article on character thoughts. (You may want to read through the comments too.) If it doesn’t provide the specifics for what you’re looking for, let me know.

  2. Thanks for another great post. I have a question about my use of parenthesis. In my current project, I use the following sentence:

    “Over the period of time I flew missions in I Corps; our AO (Area of Operations) my helicopter was shot down eight times.”

    Quite the distraction, I think. My question is, might it be better for me to put all acronyms, and there are many of them, in a glossary/appendix, as opposed to piecing them out, one by one, in the text of my book?

    • Aaron, let me ask a question or two.

      Is this character speaking to someone or thinking this? (I’m not sure if you’ve used quotation marks to indicate dialogue or if they’re there to set off the text as an example.)

      If dialogue, definitely don’t explain. Not this way. If the character is talking to someone and the other character screws up his face because he doesn’t understand the acronym, then the first character can explain. But you’d have to write out all of that, the exchange between the characters.

      If this is simply narrative, then the question becomes who is the character telling or thinking this to?” Does he recognize that someone is listening to his thoughts? If he’s just thinking to himself, maybe replaying a memory, then he wouldn’t be explaining. Not to himself. Instead he’d use the words or acronyms that he would normally use. And if he did use acronyms, that would be when you’d need to make sure the reader understood them, perhaps having a character using the full words in the next sentence when he talked to a civilian. Because this isn’t nonfiction, you can’t simply put parentheses around the text as a means of explanation.

      Before you decide how to explain all those acronyms, you need to decide who the character is speaking to and how. Typically you wouldn’t explain by putting the full words in parentheses (or, conversely, by putting the acronym in parentheses). If the character is making a snide comment about the acronym, then it’s okay to use an aside. Otherwise you have to make the meaning clear in other ways.

      Does that make sense?

      If I were remembering events, I’d use words I was familiar with to describe those events. But I wouldn’t need to explain to myself what the acronyms stood for. And even if I were telling a story to someone else, it isn’t likely that I’d use acronyms in one sentence only to translate them in the next. That is, if I were telling a story, I’d adjust my word choices to my audience.

      The point is, you want to tell the story from the narrator or viewpoint character’s POV. And that means using the words they’d use. You may have to fudge at later points to explain some phrases or acronyms, but you don’t want to sound as if you’re explaining or teaching.


      One simple way around the possible confusion surrounding acronyms is to use fewer of them. My helicopter was shot down eight times while I flew for I Corps. Or maybe When I was with I Corps, I was shot down eight times.


      So the short answer is to not use parentheses to explain your acronyms.

      • Hello Beth,
        This is an introduction to the book. I used the quotation marks, probably un-necessarily, to separate text in the book from the main body of my question. The introduction is meant to clarify to the reader that the book is fiction, based on true events. I didn’t provide any context, but the sentence is part of a paragraph stating that some helicopter aircrew members were killed on their first mission, while others seemed to be bulletproof.

        I like your suggestion, when writing dialog, to have one character use the acronym, and another use the full word version. There are some occupations wherein acronyms are used extensively. The armed forces go crazy with them. To make the dialog as realistic as possible, while writing in a way that gives civilians a fair chance of understanding what is being communicated, will be more of a challenge than I previously anticipated. I’ll find a way to make it work.

        By the way, when I finish this project, I intend to take you on as my editor. I’ll set my ego aside, and rely on your impeccable guidance.

        Thanks for your reply.

        • Aaron, there are multiple ways to write around explanations for acronyms and other issues. What’s important is that you never want to sound as if characters are explaining to readers—they shouldn’t be aware of readers at all as they’re going through their lives.

          I look forward to seeing your work when you’re ready.

  3. Mark Schultz says:

    Another great post, every writer needs this information – a squirrel just ran up the tree, he is still after the bird food- if they want to write well. ( People who are distracted easily really annoy me.) Thanks so much for allowing us to sip from the fountain.

  4. If a speaker is interrupted but is in the process of asking a question such as “Can you—” it seems as though a question mark would be appropriate. However, it is my understanding that no punctuation is to be used with the em dash. I know I can set my own style but what do you think?

    • Frank, while I have seen both question marks and exclamation points between a dash and a closing quotation mark in published books, I personally see no reason for them. The dash replaces everything that was omitted, included punctuation. We would never include other punctuation, including a comma or a period, so why include a question mark or exclamation point? The question or the exclamation is unfinished.

      If you’re going to show an interruption in dialogue, that interruption should be complete, in my opinion. The sentence should break where the speaker stopped talking. The Copyeditor’s Handbook points out that in addition to the period, question mark, and exclamation point, both the em dash and the ellipsis are acceptable terminal punctuation marks when dialogue is interrupted. Therefore there’s no reason for additional punctuation.

      I can’t find any source that recommends an exclamation point or question mark between an em dash and a closing quotation mark, although CMOS and Grammatically Correct both say that you could include either of them before the second of a pair of dashes—

      She mentioned that she needed to leave early—can you believe that?—but then she stayed till closing time.

      That’s a different situation, of course, but it’s one unusual combination that is allowed.

      You wouldn’t be the only one to ever add the question mark or exclamation point after interrupted dialogue, but there’s really no reason to use it. Readers likely understand, without additional punctuation, that it was a question that was cut off.

      • Excellent answer. Most clear and succinct.
        I have trouble getting people to get rid of a lot of punctuation in fiction that is just not necessary, the reader being able to fill it in if necessary, albeit unconsciously for the most part. I like Cormac’s paucity of commas.
        At the moment the semicolon and ellipses are plaguing me. Why people want to use them of abuse them, is beyond my ken.

  5. Phil H says:

    How about physical interruptions?

    Her index finger was out and had already landed in the middle of his chest. “I’ve had it with you! She called you (poke), on a private number – poke- that no one else has, poke, and you think it’s funny?”

    Which one is best or usual? Apologies for the iPad em dashes.


    • Phil, interruptions to dialogue—whether they are physical actions or thoughts or descriptions—are formatted the same way. The interruption must be outside the quotation marks of the spoken words. The interruption is set off by a pair of em dashes.

      “I’ve had it with you! She called you”—poke—“on a private number”—poke—“that no one else has”—poke—“and you think it’s funny?”

      For these pokes to work correctly, we probably should have seen a full poke described in an earlier sentence. Otherwise readers might not understand who was poking what. Also, since such a format introduces a lot of punctuation, it’s likely that you wouldn’t have multiple sentences with multiple interruptions. It’s not that you can’t use such a format—and doing so may make a sentence really pop—but you wouldn’t want multiple lines of dialogue with multiple interruptions in the same paragraph or maybe even on the same page.

      The same kind of setup with an interrupting thought—

      “I’ve had it with you! She“—I couldn’t believe I was acting like the proverbial shrew—“can have you.”

      • You are so good. The thing about the way you’ve punctuated it is that it’s clear to the mind and crisp to the eye. And you point about establishing the poke earlier is really smart and easy to do. Plus, the problem of too many uses of such a construction can dilute its effectiveness and begin to come off as a tic of the writer, an affectation, perhaps.

        • I try to cover as many details as I can in the limited space of a comment, but sometimes those comments do get wordy. There are so many related elements that it’s difficult to isolate only one.

          That interconnectedness is one of the reasons I love fiction so much.

          • Love, yes. The written word is a felt experience that helps us live our lives better. What makes it the supreme art form is its ability to get into the mind naturally, immediately, and without notice (except for reader-writers). You may not remember but Andy Warhol married his tape recorder; were he to do it today it would be his computer–a mistress unequaled.

      • Phil H says:

        Thanks! That is a big help. The finger in the chest is an established character trait that is usually described as poised, or landing, and with how much velocity.

        “Dialogue goes here,” she poked him lightly/angrily/forcefully with her embedded index finger for punctuation, She punctuated her remarks with several angry pokes of her index finger, or a variation of those. That example assumes the finger has already landed. I wanted to use the shove effect to make a particular conversation pop, as you mentioned. Continuous or frequent use of that mechanism would annoy the reader and writer quickly. For the opening round of a showdown in an elevator when enough is enough? I thought it would be worth it for impact value, and it seemed to help land the points better than the usual pause effects.

        Thanks again!

        • Phil, I think the sentence works quite well for your intentions. The repetition is emphatic and—as we’ve already mentioned—as long as this method of repetition isn’t overused, it should create a strong moment in your story. From what I can tell, you’ve made a great choice.

  6. I am proofreading-editing a major novel by a major novelist and have begun to question my judgment, especially with dashes and dialogue interruption. Here is an example (adjusted from the original, of course): “Where did you get this—” Tom pointed at the gun “—sorry thing?”
    I thought it should be punctuated in this way: “Where did you get this”— Tom pointed at the gun—”sorry thing?”
    The placement of the dashes and the extra spaces in the interruption itself are not what I’m accustomed to. Is my head screwed on too loose?

    • The dashes go outside the quotation marks, the quoted dialogue inside. I’m not sure if you included the extra space before Tom (in your version) on purpose or if it was just fast typing, but the sentence should read

      “Where did you get this”—Tom pointed at the gun—“sorry thing?”

      No extra spaces anywhere.

      Frank, I know what you mean about questioning your judgment. If you look at something too long, everything looks wrong.

      • Thank you, dear Beth. The author is one who just doesn’t make mistakes–or does so rarely that I’m surprised. I try always to defer to the author when possible. This author is a long-standing relationship who appreciates my neurotic drive for perfection but I did begin to question the usage until I got dizzy. It’s good to be to risk offending a great writer and find the writer receptive.

        • Great relationships between writer and editor are a delight. That deep trust—when you know the other person will freely make suggestions—fosters daring and creativity.

          I have seen the format that your author used, so maybe he was just copying what he’d seen somewhere else.

          • Author just emailed “Frank is right, as usual.” It’s nice to be right but being wrong is a valuable lesson. Learning is good.
            Do you have the St. Martin’s Style Book? I’m thinking of getting it.
            Thanks again, Beth.

  7. Robert says:

    I’ve published several novels and lead workshops in writing the novel. Your entry on the offsetting comma, em dash, and parentheses is truly masterful. You blog is one of my primary resources when I need to point developing writers in the right direction. Thanks!

  8. Ok, everyone is going to love this question. What do you do when your fiction novel is written from the perspective of an original author/writer speaking to the reader / his audience?

    Example: Daniel (me), I’m the author, but my fiction novel is about Max who is, as a character, supposedly the original author of the work I’m writing, or at least the bulk of it. Think of this fictional novel as an onion with layers of authors and stages of development. Not an easy task to write for, in my opinion.

    So in the narrative, Max’s written statement is:
    Everyone in my family are devout Baptists. Religion has always been a core belief for the Callaghan Clan. We pray (constantly it seems), attend church services regularly, and many of our best friends are people we know from our congregation.

    In the above example “constantly it seems” is used as a parenthetical aside, since Max is making a side comment to his audience about prayer.

    Max also provides a list of his siblings, which also includes parenthetical asides, as:
    My brothers and sisters, in chronological order, are:
    Christian (we call him Chrisy), born in 1985;
    Ruth (we call her Ruthy), born in 1987;
    Aaron Zechariah (just plain ‘Aaron’ or ‘doofus’), born in December of 1989;
    Hailey, born in 1991;
    Emily, born in 1993;
    Jacob (called Jakey), born in 1996;
    Wilhelm (on his birth certificate) but everyone writes his name as William (some call him Bill, we call him Billy), born in 1997;
    and Mary, born in 1997.

    Also using the ‘horrible’ semi-colon in this list.

    Again my manuscript is about a young writer, fresh out of university, named Max and the story is about Max creating this fiction novel the reader is reading. In the plot Max dies, but in his final days he asks me (the publication author) to finish and publish his work. Hence the reason he’s the speaker to his audience, the original author, while not the final author.

    Yes, again, Max is fictional, while I am a very real person. So in the sense the work blends fiction with fact. As the author I state that the novel is a work of fiction, of course. Max is also supposed to have given me his rough drafts, without the work having been completed, and many parts supposed to be under-developed or even missing. That means at times in the body matter I, Daniel, will need to be the one addressing the reader.

    As a supposedly very young writer Max’s writing, by necessity, needs to demonstrate a roughness and lack of definition and polish that an experienced author would demonstrate. All of this has to be conveyed to the reader.

    While I am writing this fiction novel as fiction, by the end of the book I want the reader to hope that it is in fact a real non-fiction work and that they (the reader) are being dupped. One of the core constructs behind the book is to stress that it is fiction (mostly in the preface, introduction, and prologue) regardless of whether or not it is the real author, Daniel, speaking or the character of Max (the fictional author) speaking.

    In the body matter, when Max is speaking, while he narrates as if it is a fiction novel, his delivery of the narrative should appear to be a work of non-fiction. That and the juxtaposition of authors is the mechanism by which I am trying to manipulate the reader into believing the fiction novel is actually a non-fiction story.

    I hope this doesn’t confuse everyone to the point of insanity. LOL

  9. Mirth says:

    Hello Beth,

    First things first—I’ve been following your site since 2011. I hope you’ll be happy to know that everyone who’s read my writing commends me on it, and it’s all thanks to you. Every question I’ve had over SPaG, plot, story flow, character development, worldbuilding, vocabulary choice, and more, you’ve answered. Crafting these entries is a tremendous work of love, and I’m for ever grateful that you’ve dedicated so much of your time to helping out all the writers and editors out there.

    For the first time ever, I’m posting a question today. There’s something I’ve been wondering about the em-dash. Let’s imagine we’ve got a character who, due to nerves, has a live of dialogue that’s riddled with false starts and aborted sentences. Like so:

    “What—no! I mean, that’s—that’s not actually—I’m not—he’s—that’s not my fault anyway.”

    Was I correct in making all the sentences/half-sentences not be capitalised? Or is there a case in which the sentence directly after an em-dash is capitalised, proper names notwithstanding? I saw once in another editing blog—can’t remember which one—that if a character stammered, every cut-off sentence should end with an em-dash, then the new sentence should start with a space and a capital letter. Like this:

    “What— No! I mean, that’s—that’s not actually— I’m not— He’s— That’s not my fault anyway.”

    The new sentence rule wouldn’t apply in the case of “that—that” because it’s a repetition but still part of the same sentence. Are any of these rules accurate?

    • Mirth, I’m delighted to know that the blog has been helpful for you. Thanks so much for your kind words and for letting me know.

      There are a couple of options for the condition you’re asking about.

      If a character interrupts himself and drops what he was saying and begins a new sentence, you can insert a space and use a capital letter to begin the next sentence.

      “I heard that Bob and Janis fought madly over the divorce. They argued so loudly that— Never mind. I shouldn’t be saying such things.”

      That’s a pretty rare construction since we often add an action beat or a thought after self-interrupted dialogue, but it’s definitely a legitimate option. Use this option to show a true interruption, to give the feel of the dialogue stopping and heading in a new direction.

      On the other hand, Anne Stilman in Grammatically Correct shows an example of a paragraph from Emmain which phrases and independent clauses separated by an em dash touch the text on both sides of the dash. In the example there’s one sentence that begins with a capital letter (no space separating it from the dash that interrupts the sentence before it), but there are also phrases that don’t begin with capitals. Thus there’s a mixture of the two options—caps and no caps—that you’ve presented, although there is no space after or before any of the em dashes in her example.

      Quoting Stilman: The dash also serves to indicate speech that is scattered or faltering: that is, not interrupted by a second speaker, but by the speaker breaking off a thought and starting another, or talking in disjointed sentence fragments.

      I’d suggest using this option—running the words into the dashes—for your example as a way to show scattered and fragmented thoughts and speech; it creates a certain feel and style. However, running the text and dashes together without spaces and caps might be a better fit when the phrases are actually phrases and not independent clauses. For your example, you could just as easily add a space and capitalize the first words that follow the dashes. Still, the format will depend on the feel you want to create. If you want to accentuate that the words stop and/or that the direction of the speech changes, use spaces and capital letters. If you want to indicate that the words are running together, even though the character’s thoughts may be disjointed, try connecting the phrases by skipping the spaces and the capital letters.

      I suggest not going overboard with the dashes and maybe not using so many short phrases in any single section of text. The visual of the dashes so close together and the repeated stops and starts could be distracting and annoying for readers.

      To remove a couple of the dashes from your example, consider something like this—

      “What? No! I mean, that’s—that’s not actually— I’m not— That’s not my fault anyway.”

      As I mentioned, you may want to differentiate between phrases and the beginnings of independent clauses that get cut off. So for phrases and single words, you may want to skip the spaces and capital letters. But when a new sentence actually begins, you may want to instead add the space and a capital letter after the interruption.

      “But it was awful. The smashed cars—the eighteen-wheeler on its side–oh God, the pigs screaming . . .”

      So you’ve got options. If you’re truly interrupting the dialogue and sending it off into another direction (and interrupting only once), a space after the dash and a capital letter to start the next sentence works just fine. If you’re showing scattered speech and disjointed sentence fragments, you can run the text and dashes into one another (with caps or without them). If you’re interrupting dialogue but you’re using independent clauses rather than sentence fragments, play with the options. Use spaces to create pauses, but forgo spaces to create a sense of panic or the feel of a character rapidly changing direction in speech.

      Does this help or confuse the issue?