To write a thriller novel, give your hero a threat they can't walk away from and a deadline they can see, tell the reader about the danger before the hero knows it, and end a good share of your chapters with that danger still open. We read the last lines of all 119 chapters in six classic thrillers: 48 of them, about 40%, stop on an open threat, a reveal or a chase. The rest let the reader breathe. Even The Thirty-Nine Steps ends half its chapters at rest.
How to write a thriller: what the usual advice says (checked November 2026)
| Source | What it tells you |
|---|---|
| Reedsy (13 Sep 2025) | Seven steps: characters and motives, start with action, show the stakes, make it hard for the hero, twists, build to the climax, a satisfying ending. No counts from real books. |
| NY Book Editors (July 2019) | Plot over story, a villain as full as the hero, open on the day the hero's life turns, clues instead of deus ex machina, twists in act 3. |
| Dabble (Doug Landsborough, 20 Apr 2023) | The opening and the climax are the two scenes that matter most; about 80,000 to 100,000 words for a first novel. |
| Lee Child, NYT Opinionator (8 Dec 2012, reposted by TVWriter) | "As novelists, we should ask or imply a question at the beginning of the story, and then we should delay the answer." |
All four agree on the ingredients. None of them says how often a thriller should leave the reader hanging, how present the clock should be, or how early the danger lands.
Chapter endings in six classic thrillers
We split six Project Gutenberg thrillers into their chapters and read each chapter's last lines. An ending counts as open when it stops on a danger not yet met, a reveal that raises a new question, someone hunted or in flight, or a threat spoken aloud. It counts as at rest when the scene is settled: sleep, a meal, a reflection, an escape completed, a joke. The judgement is ours, made one ending at a time.
| Book (year) | Words | Chapters | Words per chapter | Endings open | Share open |
|---|---|---|---|---|---|
| The Man Who Was Thursday (1908) | 57,350 | 15 | 3,823 | 10 | 67% |
| The Thirty-Nine Steps (1915) | 40,760 | 10 | 4,076 | 5 | 50% |
| Greenmantle (1916) | 98,269 | 22 | 4,467 | 10 | 45% |
| The Scarlet Pimpernel (1905) | 85,540 | 31 | 2,759 | 13 | 42% |
| The Riddle of the Sands (1903) | 107,476 | 28 | 3,838 | 8 | 29% |
| The Secret Agent (1907) | 90,202 | 13 | 6,939 | 2 | 15% |
| All six | 479,597 | 119 | 4,030 | 48 | 40% |
Source: KudoNovel's count of the Project Gutenberg texts (Thursday, Thirty-Nine Steps, Greenmantle, Pimpernel, Riddle of the Sands, Secret Agent), 11 November 2026. Words are counted between chapter headings, so a chapter's title line is not included. Six books chosen because they are public domain and still in print as thrillers; they are a sample, not the genre.
No book hangs every chapter. The most relentless one, Chesterton's, still lets five of its fifteen chapters close at rest, on a joke, a fainting fit of relief or a girl cutting lilac. A reader who is yanked at the end of every chapter stops believing the yank. The open endings work because the reader has just been allowed to sleep with Marguerite in the Pimpernel's chapter 17 and is jolted at the end of 18 by a gold ring she picks up off her husband's study floor, engraved with a small star-shaped flower.
The open endings cluster where the plot turns. In The Thirty-Nine Steps, chapters 7, 8 and 9 all end open: the Greek Premier shot dead, "The Black Stone," and Hannay "tearing past the moonlit hedgerows of Kent." In the Pimpernel, chapters 24 to 29 are five open endings out of six as Chauvelin closes in on the beach. Put your hooks in runs where the danger is closing, and rest the reader between runs.
Long chapters were normal. The average chapter here is 4,030 words, against 2,005 in Pride and Prejudice by the same count. The short-chapter habit of modern airport thrillers isn't in these books, and they still kept readers up. We didn't count modern thrillers, so we can't say how today's books compare; what the table shows is that a 4,000-word chapter can still pull.
Is The Secret Agent a failed thriller?
No, and it shows a second way to build suspense. Conrad ends 11 of 13 chapters at rest, most of them in a dim shop or a dark bedroom ("Put it out," Mr Verloc says, twice). The pull comes from what the reader knows and the characters don't. That is Hitchcock's bomb under the table, as he put it to François Truffaut: "In the first case we have given the public fifteen seconds of surprise at the moment of the explosion. In the second case we have provided them with fifteen minutes of suspense" (quoted by David Bordwell, from Hitchcock, 1967, p. 52).
A hook at the chapter's end asks the reader to turn the page. A danger the reader can see and the hero can't makes every quiet scene tense. A psychological or domestic thriller can live mostly on the second. An on-the-run thriller needs both.
The ticking clock: how often time is named
Most guides tell you to add a ticking clock. We counted how often each book names time pressure: minutes, hours, seconds, o'clock, half-past, midnight, tonight, tomorrow, dawn, in time, too late. Per 10,000 words:
| Book | Clock words per 10,000 |
|---|---|
| The Thirty-Nine Steps | 39.3 |
| The Scarlet Pimpernel | 29.9 |
| The Riddle of the Sands | 25.7 |
| Greenmantle | 23.9 |
| The Man Who Was Thursday | 17.4 |
| The Secret Agent | 13.0 |
| Pride and Prejudice (baseline) | 13.6 |
Source: the same texts, same date. A word list catches some innocent uses ("tomorrow" at breakfast), so read the numbers as a comparison between books, not an exact count of deadlines.
The Thirty-Nine Steps, the chase novel, names time nearly three times as often as Austen. Its whole plot hangs on a date (Karolides in London on the 15th of June) and a high tide at 10.17 p.m. Hannay checks his watch, catches trains and counts days, and the reader counts with him. The Secret Agent sits at Austen's level: its clock is the reader's knowledge of what is coming.
A ticking clock is not one line in chapter 2 ("they have until Friday"). It is the hero looking at it, missing a train because of it and losing an hour to someone else's lie, again and again, so the deadline is in the reader's head on every page.
How early the trouble arrives
| Book | First danger the hero can't walk away from | Where it lands |
|---|---|---|
| Greenmantle | the mission, and the dead agent who had it was Sir Walter's son (end of ch. 1) | 3.5% (3,478 words in) |
| The Thirty-Nine Steps | Scudder dead on the floor of Hannay's flat (end of ch. 1) | 11.4% (4,638 words) |
| The Man Who Was Thursday | Syme elected to the anarchists' council (end of ch. 3) | 17.6% (10,121 words) |
| The Riddle of the Sands | "And he tried to drown me" (end of ch. 8) | 26.4% (28,377 words) |
| The Scarlet Pimpernel | Chauvelin's threat to Marguerite's brother (end of ch. 9) | 28.0% (23,985 words) |
Measured at the end of the chapter where it lands. The two slower openings spend their first quarter on something else: Childers on sailing, which he uses to make the sands themselves a threat, and Orczy on Marguerite's marriage, which is the knot the whole plot pulls on. "Start with action," as the usual advice puts it, is one way. The other is to make the opening's slow material the thing that will be in danger later.
How to end a thriller chapter: before and after
A chapter ending that rests:
Hannah locked the ticket office at six, walked the long way round the harbour, and was asleep before the late ferry came in.
The same ending, open:
Hannah locked the ticket office at six. On the walk home she counted the cars in the harbour lot out of habit: fourteen, the same as every night. Then she counted again. Fifteen, and the new one had its engine running.
The second version keeps the reader in the same quiet place and adds one thing that doesn't fit. Most of the open endings in our count work this way: a voice heard before (Greenmantle, ch. 10), a smile on one side of a face (Thursday, ch. 10), a ring engraved with a star-shaped flower (Pimpernel, ch. 18).
A hook ledger to copy
Keep one line per chapter. When the draft is done, read the last column top to bottom.
| Ch. | What the reader knows that the hero doesn't | The clock now | Ends: open or at rest | If open, on what |
|---|---|---|---|---|
| 1 | The ticket was bought by a dead man | 3 days | open | the fifteenth car |
| 2 | — | 3 days | at rest | Hannah tells her sister nothing |
| 3 | The sister is being watched | 2 days | open | the phone line is dead |
Rules of thumb (the first two from the count, the last two our own): aim for somewhere between a third and two thirds open; let open endings come in runs where the danger is closing; never three rests in a row in the last quarter; and make sure the "clock now" column moves.
How to give the reader what the hero doesn't know
The Secret Agent gap needs a way for the reader to see past the hero. Three ways, each in these books:
- A second point of view. The Pimpernel cuts away from Marguerite to Chauvelin, and chapters 8, 9 and 10 each end on him: a smile, a threat, the hands rubbed together. The reader leaves those chapters knowing the trap she will walk into.
- A villain's chapter. The Secret Agent gives whole chapters to the police and to the bomb-maker. Use one when the villain's plan is the clock; keep it short and end it before the plan is fully told.
- A told-after narrator. Hannay and Childers's Carruthers tell the story after the fact, so a line like "I did not know then" can plant dread without breaking the first person.
For the twist itself, a rule of our own: plant it in a chapter that ends at rest, where the reader isn't on guard, and pay it off at the end of an open one.
Thriller vs mystery: which are you writing?
A mystery asks who did it and hides the answer; a thriller asks will they be stopped in time and often shows you the villain early. The craft differs: a mystery plays fair with clues, a thriller manages what the reader knows against what the hero knows. If your book is a whodunit with danger in it, our guide to writing a mystery novel counts where eight classic culprits are first named. If the danger turns physical, how to write a fight scene covers what each blow should cost.
How long should a thriller novel be?
Dabble's figure for a first thriller is 80,000 to 100,000 words. The six books above run from 40,760 (The Thirty-Nine Steps) to 107,476 (The Riddle of the Sands), so the old masters went short when the plot was a single chase. If your plot is one pursuit, the short end is enough; if it needs a midpoint reversal and a second hunter, budget the long end, and outline it fast so you know where each run of open endings goes before you draft.
Writing a thriller in KudoNovel
A thriller breaks in the middle when the details slip: the deadline was Friday in chapter 2 and Saturday in chapter 14, the villain knew about the safe house before anyone told him, the hero's wound has healed in two days. In KudoNovel the story bible holds each of those as an entry (the deadline as an event, the safe house as a place, the wound in the character's own entry) and a running summary of the whole book keeps the plot so far. Before writing each passage, the engine picks the entries that passage needs and reads the summary, so chapter 20 knows what chapter 2 set.
You write the chapter a beat at a time. Sketch the line ("Hannah counts fifteen cars"), Expand it into prose, and steer it in place with one instruction ("end on the engine running") until the ending is the hook you planned. When you're stuck for what happens next, Suggest, on an empty paragraph, offers three: one that stays in the moment, one that moves the plot on, and a twist that never breaks a fact you've set. After a Balanced or Novel Expand, the edit pass reads the draft sentence by sentence and fixes lines that contradict the bible.
Start your first chapter in KudoNovel: one free credit to try it, then one-off credit packs and no subscription. If your draft is already in Word, Scrivener or another tool, import it and keep going.