However, the parallel land storyline in occupied La Rochelle deliberately elevates progressive elements through new characters. Simone Strasser (Vicky Krieps), a German translator for Gestapo officer Hagen Forster, becomes entangled with the Resistance and enters a passionate lesbian romance with Carla Monroe (Lizzy Caplan), the American expatriate leader of the cell; their relationship develops into a focal subplot across episodes 3–8, including explicit scenes of them kissing and having sex, with Simone's arc revolving around her shift in loyalties driven by this connection.

Creators explicitly added female characters and the expanded Resistance plot because modern television "demanded" it and "you can’t do that on a U-boat," framing the addition as providing a "spannende politische Note" absent from the original film. This results in prominent LGBTQ+ representation and female agency as drivers of subplots and character development, though not the foundational premise. Reception notes the surprise lesbian leads as a key differentiator, with some German critics faulting clichéd portrayals while others praise the nuance.