La Rochelle, (occupied) France, in late 1941: The adventurous, naive German war correspondent Leutenant Werner volunteers to go aboard U-96 and experience life as a crew member on a German U-boat hunting allied convoys in the North Atlantic. Little does he know the "adventure" is going to be a nightmare trip: After sinking three cargo ships, the U-boat is relentlessly hunted down by enemy destroyers, dropping endless rounds of depth charge and making the U-boat crew go through hell. Escaping narrowly, U-96 (already on its way back home) is re-assigned to sneak through the heavily guarded Straits of Gibraltar, virtually a suicide mission. The U-boat is discovered, attacked and sent to the bottom of the Straits. However, unbeknownst to the enemy, the crew manages to survive and repair the vessel underwater. U-96 resurfaces and finally makes it home. Having just arrived, however, allied fighters air-raid the port. Half of the crew gets killed (Werner among the survivors) and the boat is sunk in the dock - this time for good.