Un agente del gobierno busca una célula de pérfidos infiltrados comunistas en Boston.
George Murphy
Inspector James 'Jim' Belden
Finlay Currie
Professor Albert Kafer
Virginia Gilmore
Millie / Teresa Zalenko
Karl Stepanek
Alexi Laschenkov / Gregory Anders
Louisa Horton
Mrs. Elaine Wilben
Peter Capell
Chris Zalenko / Gino
Bruno Wick
Luther Danzig
Vilma Kurer
Mrs. Rita Foss
Ann Thomas
Philadelphia Suspect
George Roy Hill
Nicholas Wilben
Karl Weber
FBI Agent Charlie Reynolds
Michael Garrett
Michael Dorndoff aka Frank Torrance
Lotte Palfi Andor
Anna Kafer
Ernest Graves
Robert Martin
