During World War II, the American submarine USS Tiger Shark is on a mission in the Atlantic Ocean. After receiving orders to rescue survivors from a torpedoed British hospital ship, the crew encounters three individuals: a British nurse, Claire, and two wounded men. As the submarine sails on, tensions rise within the crew due to the confined space and the stress of wartime duty. Strange occurrences start to unfold, unsettling the crew: mysterious sounds echo through the hull, equipment malfunctions become frequent, and the vessel appears to be haunted by apparitions. These incidents strain relationships among the crew members and amplify existing rivalries and suspicions.

A growing sense of dread envelops the submarine as the crew grapples with these inexplicable happenings. Commanding Officer Brice tries to maintain order and morale but struggles against the mounting fear that something supernatural is at play. At the heart of these events lies a dark secret that the vessel harbors: a connection between the submarine's past and its current predicament. As tensions escalate, Claire and some crew members pursue various clues, piecing together fragments of information that suggest a chilling history. This relentless descent into chaos challenges their understanding of reality, ultimately testing their resolve and will to survive as they confront an unseen and malevolent force lurking within their midst.