There’s also an unreal assassination scheme at the heart of The Prisoner or: How I Planned to Kill Tony Blair, but this plot wasn’t devised by a Hollywood screenwriter. The makers of this riveting documentary have no idea who decided to finger Yunis Khatayer Abbas and his brothers as threats to the British prime minister, or even what basis these unknown accusers had for thinking Blair had been targeted. It is reasonably clear, however, that American occupation authorities in Iraq held Abbas and two of his three brothers for months after they knew that the men were not involved in any plan to kill Blair—if there ever was one.

The story begins in September 2003, when American troops raided a Baghdad house and handcuffed Abbas, his father, and his three brothers as suspected members of the “Tony Blair cell.” This home invasion was videotaped by Michael Tucker, who was then making Gunner Palace, a documentary about U.S. troops in Iraq, with his wife, Petra Epperlein. Two years later the couple learned what happened to the English-speaking Abbas, who kept protesting “I am a journalist” as GIs roughed up his family. He was indeed a reporter and had made a sufficient enough stir in ’90s Baghdad to be arrested, tortured, and ultimately warned by Saddam Hussein himself to curb his writing. Five years later, Abbas was working as a videographer for Western news teams when he was arrested and tortured again. This time, both the process and its outcome were more ambiguous.

During interrogations in which a female soldier spat in his face, Abbas was told he was implicated in a plan to blow up Blair. The prisoner, whose closest connection to the PM was his recent work for Britain’s Channel 4, thought it was a joke. The punch line: nine months behind bars for three of the brothers. (The fourth was released after five days.) They were held in several facilities but spent most of their detention in Camp Ganci, a filthy tented barracks near Abu Ghraib for prisoners with “no intelligence value.” Simply by sending the brothers there, the occupation acknowledged that they were not involved in any terrorist actions.

Abbas was at Camp Ganci when the torture scandal at Abu Ghraib broke. That resulted in the arrival of a new group of better-behaved guards, one of whom became Abbas’ friend. Former U.S. soldier Benjamin Thompson is The Prisoner’s principal other voice, and he not only corroborates much of Abbas’ story but also credits the prisoner for helping to defuse tension at the camp. Yet after having done so, Abbas was taken into the “hard site”—Abu Ghraib itself—and interrogated for two weeks. Finally, he was released by an officer who told him, “sorry.”

Aside from the interviews with Thompson and the remarkably easygoing Abbas—who speaks unnuanced English that probably made him seem more ingenuous than he really is—Tucker and Epperlein had few raw materials. So they use sound effects, on-screen text, and Epperlein’s graphic-novel-style illustrations to expand the scope of their 75-minute documentary. These gambits are initially distracting, as is the directors’ failure to explain where they got the footage of Abbas’ arrest. The deepening story, however, overwhelms the film’s unfortunate (but entirely understandable) limitations. Fragmentary as it is, the tale of Abbas’ arrest and imprisonment is essential viewing. It may be decades before this country learns why its troops are really in Iraq, but right now The Prisoner shows what they’re doing there: running a Keystone Kops version of the very regime they overthrew.