Characters played by Phyllis Calvert
Lydia Heathley
Characters played by James Donald
Prof. Michael Heathley
Characters played by Robert Beatty
Maj. Sam Seagram
Characters played by Herbert Lom
Dr. Alex Leon
Characters played by Muriel Pavlow
Caroline Cartier
Characters played by Noel Willman
Dr. Dennis Bord
Characters played by Walter Fitzgerald
Sir Charles Craddock
Characters played by Patric Doonan
Brian Jackson
Characters played by Maurice Denham
Prof. Carrington (project director)
Characters played by Marjorie Fielding
Mother Heathley
Characters played by Caven Watson
Dr. Ferguson
Characters played by Herbert Lomas
George Jackson
Characters played by Hal Osmond
Agent Lawson
Characters played by Geoffrey Denton
Fisher
Characters played by Cyril Chamberlain
Insp. Carter
Characters played by Marianne Stone
Maisie
Characters played by Tucker McGuire
Myrna
Characters played by Stanley Maxted
Prof. Adams
Characters played by Douglas Bradley-Smith
Control room operator
Characters played by John Carew
Security policeman
Characters played by Patricia Glyn
Mabel
Characters played by John Lorrell
Control room operator
Characters played by John Martin
Control room operator
Characters played by Hartley Power
General Adams
Characters played by Philip Ray
Sentry
Characters played by Johnnie Schofield
Jim Barnes
Characters played by John Warren
Ted