Portugal, 1944. Recruited by British intelligence to help uncover Nazi secrets of atomic warfare, math prodigy Andrea Aspinall soon disappears into the crowds of Lisbon, hiding behind a new identity. Karl Voss, an attaché for German intelligence, arrives in the city under the purported agenda of helping the Reich, all the while secretly working to save his beloved home country from annihilation under their reign.

Two lost souls meet in a city filled with haunting secrets and deadly lies, desperately trying to find love amid assassination attempts, shifting loyalties, and heartbreaking betrayals. And when tragedy strikes, the repercussions last for decades, leading one of them on a quest, twenty-four years later, back into a sinister world of espionage long thought left behind.