James Toback opens with Bosch. Before a single word, before Vera Lockman has a face, An Imperfect Murder positions itself inside a tradition of painted moral horror — medieval hierarchies of sin and consequence, desire and its costs made visible in oil on panel. Then Brahms enters on the soundtrack. The announcement is large. What follows is a film too constrained by its own impulses to deliver on what the opening promises.

The premise is clean: Vera (Sienna Miller), a successful New York actress, wakes from a nightmare in which she has killed her drug-dealing ex-boyfriend, only to find the boundary between nightmare and the previous evening thinner than sleep suggested. The film’s natural subject — what guilt looks like when you can no longer tell whether you have earned it — is rich enough to carry something much larger than 71 minutes. Toback, who wrote and directed, prefers to circle rather than commit.

Miller is the reason to stay. She gives Vera an interior life that the script largely withholds — not through visible emoting but through the quality of her attention, the specific way she processes information about her own actions without quite accepting it. The scenes where Vera sits with what she may have done, measuring the distance between nightmare and reality, produce the film’s sharpest writing. Miller brings to them a precision that would have served a longer, braver version of this story.

Charles Grodin, in what would become his final screen performance before his death in May 2021, plays Arthur — a figure of old-world equanimity who enters Vera’s life as something between a confidant and a philosophical sounding board. The role is small and underwritten, but Grodin inhabits it with the economy of a man who has spent decades learning what he needs and what he can leave out. Watching him opposite Miller, you feel the register of a conversation between two actors who are more interesting than the scene explicitly allows them to be.

The formal gestures that work come early. Toback knows how to cut — the transition from nightmare to daylight is genuinely disorienting, not by accident. Alec Baldwin, as a detective who may or may not be interested in justice, finds the sardonic authority the role requires. The New York locations carry weight.

But the film is 71 minutes long and still overstays certain welcomes. The thriller mechanics never build tension; the question of what Vera actually did matters less to Toback than what she thinks about it, which would be more interesting if the psychological architecture were deep enough to bear the weight. It is not. The film asks its premise to work without doing the structural labor that would make it pay off.

An Imperfect Murder is worth watching once, on the strength of Miller’s performance and the particular gravity of watching Grodin in his last role — in a film about a woman trying to determine the moral weight of something she can barely remember doing. It does not fulfill what it announces. The gap between those two statements is the film.