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。During a traumatic accident whilst on a deep-sea dive in the depths of the Atlantic Ocean, Olive, a gifted, young marine-biologist discovers an unearthly creature. Loosing her dream job, Olive smuggles the creature home, intent on studying it in her basement, unbeknownst to her devoted boyfriend Matt. Whilst struggling to re-adjust to landlocked life and recover from her recent trauma, Olive begins to realize that she and the creature share a symbiotic bond that drives her to carry out its sinister will. Plagued by gruesome nightmares, her fractured memories of what happened during the accident in the depths of the ocean begin to unravel and reveal an eldritch horror far older and malevolent than she could ever imagine, one which she has unwittingly set free. Olive's obsession leads to madness as her discovery consumes her entire humanity, with deadly results for those around her.
