The chance meeting on the night train would lead Jeannie Rousseau to join Lamarque's operation and become one of the most effective -- if unheralded -- spies of World War II. Her precise reports on the German's secret military plans, particularly the development of the V-1 flying bombs and V-2 rockets, helped persuade Prime Minister Winston Churchill to bomb the test site at Peenemunde and blunted the impact of a terror weapon the Nazis had hoped would change the course of the war. Her exploits later landed her in three concentration camps, which she survived without ever disclosing the great secret she had stolen from the Germans.