Suspect

Tony Britton

Dr. Robert Marriott

Virginia Maskell

Dr. Lucy Byrne

Ian Bannen

Alan Andrews

Kenneth Griffith

Dr Shole

Peter Cushing

Professor Sewell

Thorley Walters

Special Agent Prince

Donald Pleasence

Parsons, alias Bill Brown

Spike Milligan

Arthur, lab orderly

Raymond Huntley

Sir George Gatting the Minister of Defense

Sam Kydd

Slater

Roy Boulting

Writer

John Boulting

Director