Amid World War II's chaos, young Spanish Communist María Millán loses her mother and brother, fleeing to France. There, after her father's death and a change of identity, she joins the French Resistance. Captured in Lyon, she's sent to Ravensbrück. Meanwhile, Hans Kammler leads a top-secret Nazi project, "Die Glocke," a time-travel technology. After the war, Kammler vanishes with the secret. María, now Maria Sliva and a KGB agent, must find him to prevent the secret from falling into enemy hands. Her quest spans from Madrid to the Vatican, unveiling dark truths and dangerous betrayals.