How to Write a Subplot, From McKee, Snyder and Seger

To write a subplot, give a second character line its own goal, conflict and ending, tie it to the main plot's theme or its conflict, and resolve it before or inside the main climax, so it changes how the main story ends. A subplot is a smaller story that runs beside the main plot. It has fewer scenes and lower stakes, but it is a complete story, not a scene or two of colour.

The three writers below cover the craft between them. Robert McKee sets out what a subplot can do in Story (1997). Blake Snyder named the B story in Save the Cat! (2005). Linda Seger gives a chapter to it, "What Do Subplots Do?", in Making a Good Script Great (third edition, 2010). All three wrote for film; the rules carry straight over to the novel.

What Is a Subplot?

A subplot is a secondary line of action with its own beginning, middle and end, usually led by a different character or a different want of the protagonist. Seger opens her chapter with what it adds: a "workable subplot adds dimensionality to a script." Subplots, in her words, "give the protagonist an opportunity to smell the flowers, to fall in love, to enjoy a hobby", so the hero becomes a person rather than a function of the plot.

What it is about is wide open. Seger: "Subplots can be about almost anything." The love story is the most common one, and she notes that "most films of any genre have a love story subplot".

What Is the B Story?

The B story is Blake Snyder's name for the main subplot. In his beat sheet it is its own beat: "The B story begins on page 30. And the B story of most screenplays is 'the love story.' It is also the story that carries the theme of the movie." He also gives it a job for pace: "The B story gives us a breather."

His example is Legally Blonde. "The B story is Elle's relationship with the manicurist she meets in Boston", and it is the place "from which she'll draw the strength she needs for the final push into Act Three". The B story often brings in "a brand new bunch of characters", people the reader didn't meet in the opening.

Snyder's page numbers are for a 110-page screenplay. In a novel, the useful part is the order: the B story arrives as the main plot moves into its second act, and it feeds the hero's turn before the climax. The rest of Snyder's beats are in the Save the Cat beat sheet.

What Does a Subplot Do for the Main Plot?

McKee gives four "possible relationships" between a subplot and the central plot. Each is a different reason to write one.

His Controlling Idea is the story's meaning in one sentence, which is how he defines a story's theme. He ranks the last one first: "This fourth relationship is the most important: use of the subplot as an additional source of antagonism." A subplot that complicates puts a new obstacle in the hero's way, so it can't be cut without the main plot getting easier.

He also warns about balance, in his pages on the setup subplot. The balance of emphasis between central plot and subplot "has to be carefully controlled, or the writer risks losing focus on the primary story." And: "A setup subplot is particularly dangerous in that it may mislead the audience as to genre."

Should a Subplot Mirror the Main Plot?

It can, and the classic case is King Lear. A. C. Bradley, in Shakespearean Tragedy (1904), writes that Gloucester's story with his two sons "simply repeats the theme of the main story": another old father who wrongs the child who loves him and favours the one who betrays him. The repetition, Bradley says, makes Lear's fate feel like a law of that world rather than bad luck.

Two things are often left out when this is quoted. Bradley calls the exact repetition "in Shakespeare without a parallel", so he saw it as rare, not as the rule. And McKee's first relationship is the opposite of a mirror: a subplot can contradict the main plot's idea. A love story that ends happily beside a main plot that ends in loss is a deliberate irony, not a mistake.

How Many Subplots Should a Novel Have?

Seger's count for films: "Most films will have at least one or two subplots. Some films may have as many as five or six." A novel has more room than a film, but the test is the same for each one. If cutting it changes nothing in the main plot, it is decoration.

An ensemble or multi-viewpoint novel carries more than a single-viewpoint one, because each viewpoint character's line is a thread of its own. Count the threads that change the ending, not the threads on the page.

Where Should a Subplot Start and End?

A subplot starts once the main plot is moving, and ends at or just before the main climax.

• Start it after the main plot, as a rule. Snyder's B story begins as the second act does. McKee: "Each subplot has its own Inciting Incident", the event that starts that thread, and the inciting incident of the main plot usually comes first. The exception is McKee's setup subplot, which opens the book when the main inciting incident has to come late.
• Bring the main subplot in early enough. Seger's warning case is Out of Africa. A strong Karen-Bror subplot "that then drops out" comes first, and the major one, Karen and Denys, "doesn't begin until late in the story (around seventy minutes into the film.)" Readers settle on the threads they meet first, so the subplot that matters most should not arrive last. Once it starts, keep it on the page.
• Close it before the main plot. When threads are nested, the last opened is the first closed, which is the nesting rule from the MICE Quotient. A subplot that resolves well after the climax risks giving the book a second ending; a closing beat in the last chapter is fine.
• Let it pay off. The strongest subplot resolution changes the climax: the ally arrives, the lie is exposed, the lesson learned in the B story is what wins the A story.

A Worked Example

Nell runs her late mother's bakery. The main plot is money: the bank wants the debt paid by September. The subplot is her sister, Jo, who has come home after ten years and wants her half sold. It complicates the main plot (McKee's fourth relationship), and it resonates its theme: what you hold on to.

1. The bank letter (main plot). The bank gives Nell until September, or it sells the bakery.
2. Jo comes home (subplot). Her sister wants her half of the bakery sold. A second obstacle, from inside the family.
3. The wedding order (main plot). One big order could clear the debt. Then the old oven dies.
4. The recipe book (subplot). Jo finds their mother's recipe book, and stays one more night.
5. The papers (subplot closes). Jo tears up the sale papers. She is staying.
6. The night bake (main plot closes). The sisters bake the order by hand until dawn, and the bank is paid.

The subplot closes one scene before the main plot, and it is the reason the main plot can close: without Jo there is no second pair of hands.

How Do You Write a Subplot in Deckle?

Deckle is a novel-writing app, and its Outliner is a board of cards, one for every document in the book, each with a synopsis. Two labels turn it into a map of both threads.

1. Open the Outliner on the Draft and add a scene for each step with Add › Scene.
2. In each synopsis, say which thread the scene moves and what changes.
3. Open one scene and make two labels, "Main plot" and "Subplot" (the pencil beside Status in the Inspector's Properties opens Edit labels & statuses). Give each its own colour.
4. Set a label on every scene.
5. Switch the Outliner to its list and read the colours top to bottom. A long run of one colour is a thread that has dropped out.
6. To read one thread on its own, open Filters at the top of the Outliner and pick its label.

When a subplot scene sits in the wrong place, move it in the Outliner until the threads alternate. The same labels show in the binder too, and labels for organising scenes covers other ways to use them. To plan a subplot beat by beat, give it its own run of cards in the seven-point story structure.

Common Mistakes

• A subplot that touches nothing. If the main plot would end the same way without it, it is a side trip. Make it complicate, contradict or resonate.
• Starting the main subplot too late. In Seger's Out of Africa example, the major subplot begins around seventy minutes in, after a strong minor one has already dropped out.
• Resolving it long after the climax. The book ends twice. Close it before or inside the main climax.
• Letting it outgrow the main plot. McKee's warning: lose the balance and you risk "losing focus on the primary story."
• Treating "mirror the theme" as the only option. Bradley called Lear's exact mirror rare, and McKee lists contradiction as a use of its own.

Sources

Retrieved 26 October 2026.

• Robert McKee, Story: Substance, Structure, Style, and the Principles of Screenwriting (ReganBooks, 1997), on the four relationships between subplot and central plot. Read through Open Library's search inside (archive.org).
• Blake Snyder, Save the Cat! The Last Book on Screenwriting You'll Ever Need (Michael Wiese Productions, 2005), the B Story beat (archive.org).
• Linda Seger, Making a Good Script Great, third edition (Silman-James Press, 2010), chapter 3, "What Do Subplots Do?" (archive.org).
• A. C. Bradley, Shakespearean Tragedy: Lectures on Hamlet, Othello, King Lear, Macbeth (Macmillan, 1904), lecture VII, on the double action in King Lear (Project Gutenberg).