In Germany, young Marie Louise's foster parents commit suicide rather than face charges of treason. Marie emigrates to the US, but when she gets there she is met with contempt and suspicion because of her German nationality. She meets Davidge, who owns a shipbuilding company, and persuades him to get her a job in his shipyards, so she can prove her dedication to the war effort. One day at work she is approached by a man named Verrinder, who is in actuality a German spy. He and some fellow spies are planning to sabotage the shipyards and want Marie to help them.