James Donald
— Michael Heathley
Phyllis Calvert
— Lydia Heathley
Noel Willman
— Dr. Dennis Bord
Herbert Lom
— Dr. Alex Leon
Robert Beatty
— Maj. Sam Seagram
Patric Doonan
— Brian Jackson
Walter Fitzgerald
— Sir Charles Craddock
Muriel Pavlow
— Caroline Cartier
Maurice Denham
— Prof. Carrington
Marjorie Fielding
— Michael's Mother
Herbert Lomas
— George Jackson
Geoffrey Denton
— Fisher
Cyril Chamberlain
— Inspector Carter
Hal Osmond
— Agent Lawson
Caven Watson
— Dr. Ferguson
Marianne Stone
— Maisie
Stanley Maxted
— Prof. Adams
Hartley Power
— General Adams (uncredited)
Philip Ray
— Sentry (uncredited)
Johnnie Schofield
— Jim Barnes (uncredited)
John Warren
— Ted (uncredited)