In New York City, an insolent pickpocket, Skip McCoy (Richard Widmark), inadvertently sets off a chain of events when he targets ex-prostitute Candy (Jean Peters) and steals her wallet. Unaware that she has been making deliveries of highly classified information to the communists, Candy, who has been trailed by FBI agents for months in hopes of nabbing the spy ringleader, is sent by her ex-boyfriend, Joey (Richard Kiley), to find Skip and retrieve the valuable microfilm he now holds.