America’s love affair with LSD did not begin in Haight-Ashbury or during the summer of love, with tie-dyed flower children frolicking in city parks. Instead it was seeded in less airy surroundings; in Midwestern laboratories and government offices, where it comprised one strand of an extensive germ warfare programme. At the rustic log club-house, underneath the mounted elk’s head, revellers drank spiked punch poured by CIA factotums. Inevitably some of these victims went clean off the rails.

Errol Morris’s splendidly clammy, mysterious docu-drama Wormwood reopens the file on Frank Olson, a jobbing biochemist who fell to his death from a New York hotel. At the time (December 1953) Olson’s death was ruled to be suicide. But 20 years later evidence emerged that complicated the official verdict and prompted Olson’s family to sue the federal government. Even today elderly Eric Olson is in search of a definitive answer. He casts himself in the role of a Cold War Hamlet, haunted and harried by his father’s ghost.

Morris has spent his career patrolling these dirty tide-pools of American history; lifting up rocks, peering at the wildlife. With Wormwood, though, he appears intent on broadening his repertoire. Gone is the straight-down-the-barrel “Interrotron” camera used to frame his subjects on films like The Fog of War and The Thin Blue Line, replaced with a multiple set-up and interviews that sometimes play out in split screen. There are reconstructions here, too, with Peter Sarsgaard playing Olson Sr and Bob Balaban cast as a CIA shrink. Elsewhere Tim Blake Nelson crops up as the government poisoner complete with a speech impediment and the sort of ghastly smile that suggests he may have recently sipped from the wrong glass.



Facebook Twitter Pinterest Uncovering the dirty tide-pools of American history … Wormwood. Photograph: Mark Schafer/Netflix

I’m not sure these reconstructions add much to our understanding, but they certainly add to the film’s hallucinatory mood. Morris’s characters are like spectres, or the human equivalent of ground-fog. They drift in at intervals to cloud the narrative and make the temperature drop.

So what became of luckless Frank Olson? Did he fall or was he pushed? Infuriatingly – perhaps fittingly – we will have to wait to find out. For Morris’s docu-drama is a six-part series, commissioned by Netflix, and the Venice film festival saw fit to screen only the first two episodes, with the others to follow later in the week. What a cruel trick of the schedule. It’s like giving the audience poison and dangling the antidote out of reach, or leading us into the labyrinth then ducking out. So we’re left to blunder on, hands outstretched, past pensive Eric Olson and those dramatic reconstructions, through spooky archive footage of a 1970s congressional hearing where sleazy Colonel Ruwet – surely the villain of the piece – sits with his back to the camera, meaning that we can only see his starched collar and his bald spot and the hint of a smile when he responds to a question.

Who, then, can predict how this investigation turns out? I’m guessing that Wormwood eventually turns Ruwet to face us. I hope it names and shames his co-conspirators too; all those discreet government drones who like to do business in the shadows. But that naturally means sticking with the journey through a further four episodes, through more twists and turns and perhaps the occasional dead-end. The prospect is enticing, but that could be the drugs talking. This trip is going to get darker and stranger before the daylight is let in.