In this provocative WW II drama, an American agent sneaks into a Nazi spy ring to learn the identities of certain double-agents. The hero works for the FBI, but was born in Germany and speaks the language like a native. First he assumes a dead spy's identity and in that guise, contacts the Nazi superiors. He is then placed aboard a U-boat and sent to the US. Things go well until his cover is blown. Fortunately, he manages to escape. He then is forced to appear in a lengthy court case to help convict the treacherous spies.