Jeffrey Hunter

as Captain Bill Ranson

Annemarie Düringer

as Rolande Hertog

Nigel Patrick

as Major Julien Howard

David Kossoff

as Dr. Mulder

Rolf Lefebvre

as Hans Faber, chief spy

Larry Burns

as Martins, building porter-spy

Anthony Ostrer

Claude Kingston

as Willem Mulder

Robert Raglan

as Lt. Miller

Peter Prouse

as Sgt. Bill Parrish