Below

The Tiger Shark patrols the Atlantic Ocean when it spots survivors adrift from the hospital ship Fort James. It rescues three people: British nurse Claire Paige and two men, one of whom is wounded. One survivor notes a German U-boat seen on the surface just before Fort James was torpedoed.

Soon after the rescue, a German destroyer closes in and the Tiger Shark comes under depth-charge fire. The submarine struggles to maneuver and sustain damage while trying to evade the surface threat.

The wounded survivor is revealed to be Bernhard Schillings, a German prisoner-of-war. Brice grows suspicious of Schillings and, when the German panics and grabs a scalpel to defend himself, Brice shoots him dead.

Brice tells Paige that Tiger Shark had recently sunk a German submarine tender and that Winters, the previous commanding officer, died after surfacing to confirm the sinking. Brice explains that he has assumed command after Winters' death.

Following Schillings’ death, the crew begins to perceive disembodied voices and other inexplicable occurrences aboard the submarine. The atmosphere grows increasingly uneasy as strange events mount.

Lieutenant Steven Coors tells Odell the true story: Winters was on deck with a small group when a confrontation over firing on German survivors escalated. Winters was struck and fell overboard, but Coors says they kept quiet to protect Winters’ reputation.

Before leaving the ballast tank, Coors dies in a mysterious accident, deepening the sense that something unseen is at work aboard the Tiger Shark. The crew realizes the mystery extends beyond the ghost stories they tell.

A series of bizarre mechanical problems plague the submarine, causing loss of control and a troubling sense that the ship is moving toward the site of its own sinking. The crew starts to question Brice's versions and the possibility of a supernatural force at play.

Loomis reports seeing Winters' ghost aboard the submarine and attempts to escape through an open trunk while the sub is underwater. He is killed when he is impaled on an outside railing.

Weird Wally concludes that the submarine is haunted by a malediction that must be satisfied to escape its netherworld. His theory reflects the growing belief that not all is as it seems on the Tiger Shark.

Paige and Odell uncover that Tiger Shark mistook Fort James for a German tender and sank the British ship by mistake. They also learn that Brice, Loomis, and Coors conspired to suppress the truth to protect their records, and Winters was killed on deck to quiet dissent.

The submarine is crippled and only five survivors remain: Brice, Odell, Paige, Stumbo, and Wally. The crew steels themselves as they deal with mounting dangers and the weight of the hidden truth.

As Tiger Shark nears the Fort James wreck, Paige sneaks to the deck to signal a surface ship with a flashlight. The plan is risky, but she hopes for a rescue and a chance to reveal the truth.

Overcome with remorse for the cover-up, Brice admits the truth about the sinking and the deaths. He then shoots himself in front of the others, leaving a heavy silence as the ship continues to float near the wreck.

A British ship answers Paige's signal and rescues the four survivors: Paige, Odell, Stumbo, and Wally. Tiger Shark sinks to the ocean floor, resting beside the wreck of Fort James as the rescue completes.