At a Prisoner of War (POW) camp for Germans in the north of Scotland, Kapitän zur See Willi Schlüter (Helmut Griem) - a German submariner – challenges the authority of the camp’s embattled Commanding Officer, Major Perry (Ian Hendry). British Army Captain Jack Connor arrives to investigate what's happening at the McKenzie POW Camp.
Police Inspector Dillon (Cyril Cusack) reluctantly sets out to see an old friend, Dan O'Flaherty (Noel Purcell). Along the way, he encounters Mickey J. (Jack MacGowran), a poitín maker who, fortunately for him, is not Dillon's target today. The inspector has the unfortunate duty of serving a warrant on O'Flaherty for striking Phelim O'Feeney (John Cowley) on the head. O'Flaherty refuses to pay the fine, as he feels he has done nothing wrong, nor will he allow O'Feeney to pay it for him. Instead, he heads off to prison.
Tommy (Aneurin Barnard) and Joanne (Amy Shiels), who is pregnant, live in a dilapidated apartment complex. One day, when Tommy is in an elevator, Joanne is threatened by a group of teenagers, all wearing hoodies. Tommy watches helplessly as the gang attack his wife, desperately trying to exit the elevator. He finds her beaten, with a syringe in her stomach. In the hospital, Joanne survives and gives birth to Elsa (Harry Saunders), a healthy girl. However, Joanne remains in a coma for several months, eventually being taken off life support. Grief-stricken, Tommy is consoled by a friendly nurse, Marie (Wunmi Mosaku), who attempts to help him with his agoraphobia, the result of his traumatic experience.
James Furlong is the last in a long line of Furlongs who were each blessed or cursed with a strange ability. His grandfather, Charlie went temporarily blind when he thought about sex. His father, Philip could turn off anything electrical when he was frightened. From the moment of his violent birth, involving the death of his mother, his life seems ill-fated, but it is unclear what kind of ability, if any, he possesses. Growing up in rural Ireland, his grandmother tells him about the strange quirks of his ancestors and the boy begins to experiment on himself, longing to discover some extraordinary, hidden power. But instead, his experiments lead to the death of his family's livestock, followed swiftly by the loss of Philip and his beloved grandmother, Charlotte. By the time he is ten years old, James is the sole survivor of the Furlong family.
A mutated strain of mad cow disease infects the Irish countryside, turning people into ravenous, flesh-eating zombies. Caught amid this chaos are a young Spanish tourist and the local gravedigger. Together, this unlikely duo must fight for survival or become part of the Zombie Fest.