In all its glorious oddness, Good Boy recalls a particular boom time in British exploitation cinema for horror films that weren’t necessarily horror films, movies with titles like Mumsy, Nanny, Sonny and Girly, What the Peeper Saw and almost anything by Peter Walker. The latter’s House of Whipcord would be a useful reference when describing Jan Komasa’s thoroughly entertaining debut, since it’s a similarly dark and acerbic comedy about moral rectitude, Walker’s film being the story of a “loose” young woman falling into the clutches of a deranged former judge and his wife, who live in a private prison.

In Komasa’s case, the victim is male: Tommy (Anson Boon), a disruptive internet influencer whose TikToks advocate violence and recklessness. Tommy walks the talk, and the film’s opening salvo illustrates a typical night on the town for him. “I’m f*ckin’ buzzin’,” he declares, before embarking on a drink- and drug-soaked party night that involves masturbation, vomit, sex, more alcohol and drugs, before passing out in the street and, unbeknownst to him, into the hands of a stranger.

The person who finds out what happened to him is Rina (Monika Frajczyk), an illegal immigrant applying for work as a housekeeper at a big, remote estate in the countryside. Her employers are the genial Chris (Stephen Graham) and his quiet wife Kathryn (Andrea Riseborough), and the interview process is quite intrusive (“Do you have any children? Distinguishing marks? Tattoos?”). On her first day on the job, she is alarmed when Chris confiscates her mobile, insisting, “We don’t use phones in the house.” But she is positively shocked to encounter Tommy, shackled to a makeshift bed in the basement.

The setup is pure torture porn, and when Tommy reacts violently toward his captors, he is savagely beaten, satisfying those expectations in the short term. But soon it transpires that this isn’t really who Chris is. His backstory is hinted at but left ambiguous; suffice to say that Chris and his wife haven’t taken Tommy off the streets to kill him — they actually are trying to save him, albeit in an unorthodox and non-denominational way.

Tommy doesn’t see this at first, telling Chris, “I’m gonna rip off your skull, and I’m gonna stab you in the dick.” But when he meets their crazily cheerful son Jonathan (Kit Rakusen), Tommy realizes that there’s some kind of a salvage plan here, and that there will be a chance to escape later if he plays along.

This battle of wits is at the core of Komasa’s film, which owes a little bit of a debt to A Clockwork Orange (the book more than the film). The longer Tommy stays under the family’s roof, the more he appears to respond, plowing through the novels that Kathryn has laid out for him. He even discovers cinema, having his evening ruined on movie night by a screening of Ken Loach’s tragic masterpiece Kes. In time, he is moved upstairs into a bedroom, still chained by the neck but mobile thanks to a network of rails that allow him to move from room to room.

Like an early Yorgos Lanthimos, the strangeness of the premise does a lot of heavy lifting, but the performers literally bring character to what might easily have been a one-note movie. Boon is scarily convincing as Tommy, bringing out the twin barrels of intelligence and ignorance that make him so dangerous. Riseborough is suitably ghost-like as Kathryn, who is secretly the heart and soul of this misguided mission in which Chris is the brain. Fresh from Adolescence, though, it’s Graham who steals the show, using his newly minted everyman persona to creepy effect. Chris is like a more benign Jigsaw from the Saw movies; his weapon is his judgment, and — like a father from heaven, or indeed hell — his disappointment is something to be feared.

Title: Good Boy
Festival: Toronto (Centrepiece)
Director: Jan Komasa
Screenwriters: Bartek Bartosik, Naqqash Khalid
Cast: Stephen Graham, Andrea Riseborough, Anson Boon, Kit Rakusen, Monika Frajczyk
Sales agent: Hanway
Running time: 1 hr 50 mins