Theme

The argument under the plot — what the story believes about how life works.

Theme is the position a story takes: not 'love' but 'love requires surrendering control'; not 'war' but 'war makes monsters of survivors'. The plot is the theme's proof — the protagonist tests the belief and the ending renders the verdict.

It's felt, not announced. When a character states the theme outright, it usually lands early and slantwise (Save the Cat! budgets a whole beat for it), then the rest of the story argues it out in behavior.