Let Us Prey is a 2014 horror film directed by Brian O'Malley and written by Fiona Watson and David Cairns.
Plot
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. Whilst on patrol, Heggie witnesses Francis "Caesar" Sargison's car strike the mystery man. He disappears, and Heggie arrests Caesar. At the police station, she is greeted by Sgt Jim Macready, who charges Caesar with reckless driving. 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. Heggie phones Dr. Duncan Hume to examine him; however, upon examination Hume experiences a flashback and attempts to kill his patient for supposedly knowing what Hume has done. Hume is placed in a cell, and the unknown man is identified as having the fingerprints of an old man who died over 20 years ago. He makes several references to Old Testament justice before Macready also suffers a flashback and angrily has Heggie and Mundie place him in cell six (and for this reason the character is named "Six" in the end credits, although never referred to as such by any other characters during the film). Mundie has a flashback to beating a prisoner with Warnock.
Macready has Mundie and Warnock go to Hume's house to find his wife before Macready drives to his own home. Heggie researches the names in Six's notebook, discovering they are all deceased criminals. In the cells, Six, who displays supernatural powers, quizzes Beswick about the true reason why he beats his wife. Unsatisfied with Beswick's answers, Six induces him to attempt suicide. Caesar alerts Heggie, who allows Hume to examine Beswick, who dies after claiming to know who Six is. Elsewhere, Mundie and Warnock enter Hume's house and find he has murdered his family. 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. He hurriedly disposes of a dismembered body in his fridge along with the body of one of the men shown on the posters, whom he had beaten to death in a drunken rage.
Hume helps Heggie carry Beswick upstairs, but he attacks her when she learns about his family. After restraining him, she returns him to his cell. 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. Mundie and Warnock return and drag Hume to interrogation, ignoring Caesar's attempt to confess. As Hume confesses to Mundie about killing his family out of nihilistic boredom with his career and a desire to unlock the secret of immortality, Warnock talks to Six and has a flashback to staging the suicide of the man he and Mundie had beaten. Enraged, Warnock rushes to interrogation and brutally kills Hume in front of Heggie and Mundie. Heggie is threatened into remaining silent.
Caesar confesses to Heggie about hitting the girl, but Six says it is too late for redemption, as the girl had died two minutes earlier where Caesar left her next to the road. Heggie also has a flashback and remembers that Six had distracted her childhood abuser, allowing her time to escape. Six informs her Mundie and Warnock are planning to kill her. 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. He shoots and kills Warnock, then wounds both Heggie and Mundie as they barricade themselves in the cells. 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 offers to help her, but only if she asks him to. She refuses.