Nazi-occupied France, 1942: In the u-boat port of La Rochelle the crew of U-612 prepares for their maiden voyage when translator Simone Strasser arrives.
While the crew is itching for combat, Kapitänleutnant Hoffmann is adamant on performing more drills first. Meanwhile Simone tries to make sense of last night's events on the streets of La Rochelle.
After the enemy attack solidarity on board U-612 diminishes. Hoffmann and Tennstedt's rivalry and the ongoing tension among the crew threatens their mission.
After Greenwood departs the U-boat a new guest comes aboard in surprise and the infighting for loyalty among the crew continues. In La Rochelle the relationship between Simone and Carla grows.