Eric Erickson, a Swedish-American businessman engaged in oil trading, is blackmailed by the Allies during World War II to spy on Nazi Germany due to his neutral status and access to Germany. Initially hesitating, he agrees after being threatened with public exposure of aiding Axis powers. Erickson is partnered with Marianne Möllendorf, a brave German resistance fighter. The two work together to gather intelligence from inside Germany, focusing on strategic targets like oil refineries critical to the Nazi war effort. They tread a perilous path in Germany, where the slightest mistake could expose and endanger them.

As they forge documents and build identities to infiltrate higher echelons of the Nazi establishment, trust and camaraderie grow between Erickson and Marianne despite their differing backgrounds. Erickson struggles internally with his dual existence and the moral ambiguity of his actions, feeling isolated from both Germans who see him as an ally and the Allies who see him as expendable. His personal sacrifices deepen, creating tension and emotional strain. With pressure mounting on both sides, they face increasing scrutiny and danger. Their missions become fraught with risk as Erickson navigates a deadly landscape filled with espionage, betrayal, and the ever-present threat of discovery, all while trying to retain a semblance of personal morality amidst chaos.