The sole survivor of a blood-drenched massacre must team up with a rag-tag bunch of rookie cops and lawbreakers to defend a police station from an invasion of monsters from another dimension.

Sophie's 18th birthday party becomes a bloodbath when six terrifying monsters descend upon her house, intent on devouring the party guests and killing anyone who tries to leave. As her school friends are torn apart and eaten, Sophie must rally a band of misfits and take up arms to send their party crashers back to hell. To survive the night, Sophie will face her destiny; monsters are real - and she's the only one who can stop them.

奥丽芙是一名年轻很有天赋的海洋生物学家，在大西洋深海潜水时发生了意外事故，导致受伤失去部分记忆而失去了梦想中的工作。在那次事故中她发现了一个神秘的生物。奥丽芙私自把那生物带回了家，打算在地下室研究它，而她的男友马特并不知情。在内陆生活并疗伤的恢复期间，奥丽芙开始意识到她和这个生物有着一种共生的纽带，驱使着她去执行它邪恶的意志。由于受到可怕的噩梦困扰，她拼凑着在海洋深处发生事故时的破碎记忆，没想揭露出一个古老恐怖邪恶无法想象的秘密，已被她无意中释放出来。奥丽芙发现她疯狂的痴迷不仅危害到她，而这也威胁到了她周围的人。