A sinkhole appears at a fracking site in the woods near an esteemed but tough British boarding school, causing the pupils and teachers alike to fight for their survival against the monsters it unleashes.Don Wallace (Finn Cole) is forced by his mother Babs Wallace (Jo Hartley) to attend a boarding school called Slaughterhouse. Mr. Meredith Houseman (Simon Pegg) is the housemaster, Willoughby Blake (Asa Butterfield) is Don's new roommate. Houseman and Blake are a bit cagey about Blake's old roommate, as both find excuses whenever the topic comes up in front of Don. The school has houses, Andromeda is for girls, Xenephobes is for nerds, Olympus is for jocks, and Farta is for the losers of the school.Clegg (Tom Rhys-Harries) is a snob & school prefect and Caspar De Brunose (Jamie Blackley) is the head boy. Swimming in the lake is not allowed and woods are out of bounds. Audrey (Margot Robbie) is Houseman's crush, who was visiting slaughterhouse for just one year. Houseman misses Audrey. The Bat (Michael Sheen) is the principal of the school. A new fracking site opens on school grounds and leads to a sinkhole to open up. According to school legend, in 1330's a knight emerged to slaughter a mythical beast that was terrorizing the village and in exchange he was given title to the lands where the castle was built in 1334. The castle was converted in a school in 1770.Dom has the hots for Clemsie Lawrence (Hermione Corfield). Clegg hates Dom for eyeing Clemsie. On a morning jog, Blake, and Dom venture through the woods for a shortcut and discover the sinkhole with foul smells emanating from it. during their run they also meet Woody (Nick Frost) who is leading a protest group against fracking and warns Dom & Blake against unimaginable horrors coming out from the sinkhole. He also alleges that The Bat and the CEO of the fracking company were chums back in the school days.Unknown to Dom, Clemsie is hooking up with Smudger (Louis Strong). That night a massive earthquake rocks slaughterhouse. The same night a monstrous scream emerges from the sinkhole. Clemsie, Kay (Isabella Laughland), Dom and Blake venture out to investigate and find small, vicious rat creatures who attack them. Clemsie manages to kill one and takes it to The Bat. But he refuses to call in any authorities. Thats when one of the large rat like creatures attacks the entire group. The Bat is killed in the ensuing meddle, but the group escapes in the Bat's car. The group wants to escape, but Clemsie says she has to go back to the school to rescue Smudger as he is her brother. Dom agrees as he is relieved that Smudger isn't her boyfriend. A pack of these rats attack a frat party, where Smudger is. Clemsie and Dom rescue him, while Houseman kills one of the rats himself.Houseman decides that the group needs firepower to repel the rats. He leads the group to the school armory. But Clegg is already there and refuses to give arms to Blake and Dom, whom he hates. He shoots Houseman, who calls Audrey, but isn't able to speak to her before both he and Clegg are carried away by rats.The group now decides to hide underneath the school tunnels, where they find Woody. The rats follow the group inside the tunnels and eat Woody. The group manages to escape out of the tunnels, but Blake and Dom execute Woody's plan and set fire to the tunnels to kill all the rats. Clemsie and Dom kiss. Houseman survives.