Passport to Treason is a 1956 film set in London, England where an American ends up investigating the death of a friend. Mike O'Kelly (Rod Cameron) is a private investigator stationed in London whose life changes with the death of a friend. Mike begins investigating his friend's murder and discovers layers of deception that go far beyond London. When Mike realizes a pacifist organization may be involved in the crime, he enlists the help of undercover agent Diane Boyd (Lois Maxwell) to probe into the affairs of the group. Mike and Diane stumble onto a scheme with serious national and international implications and discover that the pacifist organization led by Orlando Syms (Clifford Evans) is not what it seems. Orlando Syms is using the pacifist organization as a front for a fascist group whose aim is to take over the world. Mike, along with Diane's help, intends to stop the group and bring his friend's killer to justice.