Robert Crain (Marlon Brando) is a wealthy German engineer and pacifist who fled to India under a fabricated Swiss identity after being conscripted into the Wehrmacht at the start of World War II.

He is blackmailed by English Colonel Statter (Trevor Howard) and the Allies into participating in a plan to seize a shipment of rubber, which is in short supply and essential for both sides' war efforts, that will soon be carried by the German merchant ship Ingo from Japan to Nazi-occupied Bordeaux.

Crain is provided with fake documentation and a cover story: he is Standartenführer Hans Keil, a high-ranking SS officer needing to return to Germany.

The first officer, Kruse (Martin Benrath), is a fanatical Party member who keeps a close eye on the captain, and the crew is a mix of Nazi loyalists and political prisoners who were pressed into service due to labor shortages.

That submarine has two German Naval officers aboard, along with a number of American prisoners and Esther (Janet Margolin), a young German-Jewish woman who has been raped and tortured by her Nazi captors.

Disgusted by this, Mueller becomes drunk and reveals in a rage the full extent of his anti-Nazi beliefs, which gives Kruse a reason to declare the captain unfit and take command of the ship.

Just before the mutiny occurs, Kruse receives the submarine radio message that Crain's SS identity is false, and arms the loyal part of the crew.

And he plays it with evident enjoyment, milking the moments of suspense with all his beautiful skill at holding pauses and letting tense thought churn behind his bland eyes.

Again he speaks with a juicy German accent, as he did in "The Young Lions," and affects the elegant air of a fellow who packs an iron fist in a silken glove.

After having appeared in a series of box office disappointments, Brando agreed to promote Morituri for the studio by participating in a day-long press junket at the Hampshire House in New York City.