The submarine U.S.S. Manta had a perfect record until the mysterious death of its captain. The next-in-command, Lt. Richard Brice (Bruce Greenwood) is determined to steer his disheartened crew back to safety. But after three battle survivors board the sub, bizarre and frightening things begin to happen. As the tale unfolds, and crew members begin to disappear, Ensign Douglas O'Dell (Matthew Davis) must piece together the puzzles of the submarine's past before it is too late to resurface alive.