In the heart of World War II, Lukas, a loyal German officer, is called upon by his commander, Colonel Jansen, to uncover a British spy in the city of Zwolle. With urgency driving his actions, Lukas arrives in Zwolle and begins his mission. As he delves deeper into the investigation, he faces unexpected challenges, from confronting captured British officers to encountering a mysterious intruder in his hotel room. With the help of the local police, Lukas narrows down his suspect list to 61 men, and a peculiar clue on a British army knife leads him to William Sebold. But when confronted with the evidence, William's reaction takes a dangerous turn, leading to a suspenseful climax that threatens Lukas's very life.