Dr. Eleanor Hartley, a thirty-eight-year-old cryptographer at Bletchley Park in the summer of 1943, discovers a hidden, intentional signal within German Enigma communications. Initially believing it to be a double agent transmitting to Colonel Hans Richter, her investigation with Major James Whitmore, an American intelligence officer, reveals that Richter is already deceased. This deepens the mystery, leading them to suspect Eleanor's supervisor, Commander Edward Holbrook, as the source. However, further scrutiny reveals ambiguity. The truth is eventually unveiled by Captain Robert Hayes of American intelligence: the signal is not from a double agent but evidence of sabotage by Colonel Wilhelm Steiner, a German officer working against the Nazi regime. Even more disturbingly, American intelligence is aware of and protecting Steiner, deeming him a vital asset for post-war reconstruction, a secret they are keeping from the British.Eleanor faces a profound moral crisis: remain silent and complicit in an unauthorized American operation, or expose it, potentially triggering an inter-allied crisis and jeopardizing Steiner's life. She chooses to report her findings to her superiors, which initiates high-level diplomatic discussions between British and American war cabinets. A compromise is reached where Steiner is quietly removed and protected, but his fate remains uncertain. Six months later, Steiner is reported dead, leaving Eleanor to grapple with the moral ambiguity of intelligence work, where pursuing truth can lead to tragedy and the consequences of decisions are never fully predictable.