The Boathouse Fire Climax (Body Heat) Body Heat (1981)

Protagonist	Ned Racine
Mission	Verify Matty around the edges of the affair without breaking the frame she is operating in
Runtime	113m
Climax	beat 39 · 103m · 91% into film
Wind-down	beats 40–43 · 104m–113m · 9m long
Resolution type	repudiation

The climax

Ned has waited in the kitchen with Edmund's gun, has sent Matty down the lawn to the boathouse to retrieve the steel-rimmed glasses she said Betty had hidden in the dresser there.^{b36 b37 b38} Matty stops at the kitchen door to say "no matter what you think, I do love you" and walks out. The audience-certainty moment is bounded to a single shot: Matty reaches the boathouse door and the structure engulfs in a single fireball.^b39 Ned screams her name from the trees.

The mission sentence Ned has been running through the back half — investigate from inside the affair, send her into the trap she set, watch what happens — resolves at the detonation. What the fireball confirms is that Matty was always one move ahead. The delayed-trigger device she commissioned from Teddy Lewis a week earlier was rigged for whoever opened the door, and the woman who walked through it was not the woman the trap was set for. Ned has been the instrument from frame one, and the moment of finally acting on his suspicion is the moment the trap consumes its second victim — Mary Ann Simpson, planted in the boathouse, dental records pre-arranged.

The wind-down differs because

The cut to the interview room ("She's alive!") and the prison-library reconstruction execute what the climax has already verdicted — Ned, in custody for two murders he did not solo, walking Oscar backwards through a long con that has no provable form, no money, no body that anyone in the room will identify as Mary Ann.^{b40 b41 b42} The tropical-beach coda flips the reading — a woman in dark glasses, the opening "It is hot" / "Yes." inverted into pleasure — and confirms the doubled quadrant: Matty's cynical fable resolves on a beach the same way Ned's tragedy resolves in a prison library.^b43 Both are new equilibrium executing, not test running.

Why this is a repudiation climax

The post-midpoint approach — investigate from inside the affair, stay in bed with the suspect while assembling evidence — is run all the way into the climax and fails. Ned never realizes in time. The kitchen scene shows him voicing the suspicion at maximum strength ("Experience shows I can be convinced of anything"), holding the gun, sending Matty to the boathouse to retrieve the glasses, and he is still inside the trap she built around exactly his late-arriving suspicion. The film's verdict on the approach is plain: investigating-from-inside was the wrong response to the perpetuities midpoint; the ideal approach not taken was the one Lowenstein and Oscar named at his apartment — leave her — which Ned refused on the record.^b27 Tonally heavy, structurally complete: the boathouse explosion is the test of a deepening commitment that was always commitment to the wrong frame. (Note: the same explosion functions as the climax of Matty's shadow film in the worse-tools-sufficient mode — see Plot Structure (Body Heat).)