Communist agents in Canada are spying on Dr. Carl Macklin, an atomic physicist whose knowledge they want. To kidnap him, Eric Hartman, the party's top man in Montreal, offers $100,000 to a deported American criminal, Joe Victor.
A member of British Intelligence assumes a fictitious criminal identity and allows himself to be caught, imprisoned, and freed in order to infiltrate a spy organization and expose a traitor; only, someone finds him out and exposes him to the gang...
In New York City, an insolent pickpocket, Skip McCoy, inadvertently sets off a chain of events when he targets ex-prostitute Candy 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, to find Skip and retrieve the valuable microfilm he now holds.
After two gang-related killings in "Center City," a suspect (who was framed) is arrested, released on bail...and murdered. Inspector Briggs of the FBI recruits a young agent, Gene Cordell, to go undercover in the shadowy Skid Row area (alias George Manly) as a potential victim of the same racket. Soon, Gene meets Alec Stiles, neurotic mastermind who's "building an organization along scientific lines." Stiles recruits Cordell, whose job becomes a lot more dangerous.
After learning that the death of his wife was not an accident, a former CIA Station Chief is forced back into the espionage underworld, teaming up with an adversary to unravel a conspiracy that challenges everything he thought he knew.