Infuriated by receiving the wrong piece of film, a meticulous statistician named James Richards arranges for the researcher responsible, Sharon Newton, to lose her job. When Sharon realizes he was behind the firing, she reaches out and demands his help. She has acquired a mysterious fragment that, on the surface, looks like nothing more than a collage of street scenes, yet it appears to capture the abduction of a woman. The reel abruptly ends, directing the viewer to seek out a film called The Hedgerows of England. Because this film has been officially registered and classified by the Ministry of Defence, Sharon, obsessed with identifying the woman, needs James’s credentials and access to information to help her locate it.
James pursues the film’s whereabouts, only to run into dead ends. A visit to an old tram depot and an archive beneath Oxford Street proves futile, for the film has already been relocated. The chase leads them from a landfill site, where a police presence looms, to an incinerator in Edmonton, where they manage to retrieve the reel just before it is incinerated. Yet when they view the film, they discover a strikingly poor quality image: a dark silhouette of a woman standing before some kind of tribunal. At the end, a card points them toward the next film to seek, titled Hop-Picking in Kent.
James’s life, once orderly and insulated, begins to tremble at the edges as the search for the film disrupts his routine. He wakes up after a drunken night spent at a video duplication service to find Sharon at his side, and to learn that she has a young daughter. With work calling, Sharon leaves her child in James’s care, forcing him into the unexpected role of guardian for a time.
Taking the baby with him to meet his ex-wife, James is confronted by two officials who beat him and press for information about something he has uncovered. Shaken, he seeks counsel from his City friend Anthony, who urges him to go home and forget about it—though Anthony also hints that he has faced questioning himself, revealing that danger is closing in on more than one person. James returns to a home that has been searched, realizing that the officials want some medical records he had idly picked up at the landfill. After a tense confrontation, James escapes and reunites with a distressed Sharon, who has been worried about her daughter.
Meanwhile, a friend of Sharon’s conducts illicit archival digging and uncovers the film Hop-Picking in Kent. Inside the plain, documentary-feeling footage lies a more complete version of the enigmatic film, featuring a different woman and a man, and hinting at a calamity that has left the participants dead. The narrative then shifts forward in time to document the birth—and abrupt abortion—of a government project named Magnificat. The woman from the original footage reappears, seated in a setting James recognizes: an official building that has reopened as a café. The film culminates with the woman reuniting with a horribly scarred man and confronting the cameraman, asking why he is filming.
James theorizes that the whole affair points to a covert, hushed-up accident involving nuclear power, with the café having once served as a secure convalescent unit. He wonders aloud why the film was even made in the first place. In the end, James and Sharon decide to keep the film’s existence a secret, and James discards the incriminating medical records in a bin. Yet the intrigue continues to haunt London: somewhere in the city, a cleaner taps into a secluded room where the remnants of Magnificat are still stored. The film is incinerated, but before that happens, it is transferred to tape, leaving parts of the footage unusually dark. The final scene, featuring the cleaner, ties back to the moment when the woman who had been tending the café reappears as James and Sharon come in toward the end of the movie. The boxes remain stored in the building where the convalescent project once unfolded.
