An FBI agent works with a refugee scientist and the Coast Guard to crack a Soviet spy ring in Boston.
George Murphy
as Inspector James 'Jim' Belden
Finlay Currie
as Professor Albert Kafer
Virginia Gilmore
as Millie / Teresa Zalenko
Karl Stepanek
as Alexi Laschenkov / Gregory Anders
Louisa Horton
as Mrs. Elaine Wilben
Peter Capell
as Chris Zalenko / Gino
Bruno Wick
as Luther Danzig
Vilma Kurer
as Mrs. Rita Foss
Ann Thomas
as Philadelphia Suspect
George Roy Hill
as Nicholas Wilben
Karl Weber
as FBI Agent Charlie Reynolds
Michael Garrett
as Michael Dorndoff aka Frank Torrance
