But what if that transparency was itself part of a larger cover-up? What if the display of accountability put on by the military and the C.I.A. was actually the opposite — a false confession intended to distract attention from a far more sinister crime? Those are the questions that Mr. Morris pursues. They are the questions that have haunted his main interview subject, Frank Olson’s oldest son, Eric, for more than 60 years.

Varying his usual head-on methods, Mr. Morris often films himself and Mr. Olson in a two-shot, facing each other across a room in Mr. Olson’s childhood home. A clock on the wall is permanently stopped between 2:30 and 2:35, the approximate time of Frank Olson’s death. The conversations — at times strangely buoyant, given the gravity of the topics under discussion — are interwoven with old photographs, home movies and television clips.

They also, more strikingly, give way to re-enactments of what is known or believed to have happened in the days just before and after Frank Olson’s death. Peter Sarsgaard plays him as a troubled man with a sensitive face and a gentle demeanor, and he’s surrounded by other well-known character actors (including Bob Balaban and Tim Blake Nelson) in what can feel like a lost, unfinished Hitchcock movie. The world of the 1950s is a somber swirl of cigarette smoke and dark shadows, where people speak in whispered riddles, drink martinis and drive around in hulking automobiles. Olson seems like a quintessentially Hitchcockian wrong man, a relative innocent sucked into a vortex of conspiracy and preyed upon by men with sinister agendas and dubious scruples.

For Eric, he is more like the paternal ghost in “Hamlet,” which makes Eric the melancholy Danish prince. Scenes from Laurence Olivier’s screen adaptation of the play flicker into view now and then, enriching both the psychological and the visual texture of “Wormwood” (and providing, along with the Book of Revelation, a source for its title.) This is, like “Hamlet,” a tragedy at once public and intimate, an examination of how the impersonal violence of the state can damage and distort individual lives.