An inexperienced U-boat crew are plunged into a perilous secret mission, while new translator Simone starts work at the base.

Hoffmann insists on further training despite the crew's desire to head to battle. In La Rochelle, Simone pieces together the previous night's events.

Tennstedt and Hoffmann continue to butt heads aboard U-612, while rebel Carla Monroe plans a mission in La Rochelle.

Unity on U-612 has crumbled and Hoffman and Tennstedt's continued conflict could jeopardise the mission. On land, Simone wrestles with a difficult choice.