A mysterious man arrives in a small town in Scotland where PC Rachel Heggie awakens from a nightmare about being abused as a child before heading out on patrol.

Heggie radios PCs Jennifer Mundie and Jack Warnock to find the victim before taking Caesar to the cells, where he joins his teacher, Mr. Ralph Beswick, arrested for beating his wife.

Mundie and Warnock, having found the man that Caesar hit, bring him to the station, mute, covered in scratches and carrying only a notebook with lists of names.

Macready is revealed to be a serial killer who seduces and then murders young men, as shown by several missing posters in the police station.

Six reveals he knows about Heggie's childhood abuse, and, when she leaves, he offers Caesar redemption if he confesses to a second hit and run accident from earlier in the night when he ran over a young girl and left her to die.

Heggie fights Mundie and Warnock, who nearly succeed in strangling her, until the sudden return of Macready, now insane, wrapped in barbed wire, wielding a shotgun and quoting verses from the Bible.

While Macready sets the building on fire, Six makes references to his true identity, of losing an argument with "an old friend" about human sin, and being an outcast like Heggie.

He crosses off every name except Heggie's and condemns the others to Hell for their various sins: Mundie and Warnock as “adulterers and betrayers who dare to weigh justice in their own hands” as the married Warnock had been having an affair with Mundie, Beswick as a hypocrite, Macready as a pervert, Hume as being “cowardly and vicious”, and Caesar for both hitting the girl with his car and being too weak to confess.

[8] The Herald wrote the film starts off slowly and has weak dialogue, but praised Cunningham's acting and the occasionally cartoonish gore, which they said make it fun.

[9] Harry Guerin of Raidió Teilifís Éireann rated it 4/5 stars and praised the acting of both McIntosh and Cunningham, who he said was perfectly cast.

[11] Andrew Marshall of Starburst rated it 10/10 stars and wrote, "Striking a perfect balance of suspense, violence, humour, story and action, Let Us Prey feels at once classic and modern".