What happens when men on a submarine find themselves facing death, due not to the deadly ocean but a malignant paranormal entity? The USS Hancock is a fleet ballistic missile submarine carrying sixteen nuclear missiles, a crew of 13 officers and 130 enlisted men. On a deep dive that takes her below test depth, the Hancock picks up one additional, unwanted sailor. When Gerhard Küehn, a ghost who has been forever reliving the sinking of his German U-Boat, suddenly finds himself aboard the American submarine, a struggle for the life of the Hancock and every man aboard her ensues.