1943; the USS Tiger Shark is a submarine on patrol in the Atlantic Ocean, but after picking up drifting survivors spotted by a UK plane, we slowly discover that all is not as it seems on the boat. Amid the tensions of remaining silent while being depth charged and the continual strain of being cooped up inside a dangerous tin can for long periods of time, things are going wrong, strange sounds haunt the boat and the mechanics malfunction. What happened to the captain? Why is the boat returning to a previous engagement like a lamb to its ewe? Are they even still alive? Or are they themselves ghosts from a previous engagement?