cast
- William Osler Mu Lambda 165 (aka: Host Computer) / Computer voice & Host
-
Keir Dullea
Devon
-
Robin Ward
Garth
-
Gay Rowan
Rachel
- James Barron Garth's Father / Computer Voice (voice)
- Aileen Seaton Rachel's Mother
-
Walter Koenig
Oro
- Scott Fisher Small Boy / #4
-
Ed Ames
Mr. Smith
-
Sterling Hayden
Old Jeremiah
- George Sperdakos Jubal
-
Gillie Fenwick
Old Abraham
- Sean Sullivan Rachel's Father
-
Kay Hawtrey
Garth's Mother
-
Alexandra Bastedo
Idona
-
Stephen Young
Dr. Chris
-
Frank Converse
Dr. Gerald W. Aaron
-
John Colicos
The Governor
-
Barry Morse
Shaliff
-
Lloyd Bochner
Col. M.P. Garoway
- David Tyrell One - Captain
- Susan Stacey Five
-
Simon Oakland
Dr. Asgard
-
Percy Rodriguez
Sakharov Richards
-
Angel Tompkins
Daphne
-
Donnelly Rhodes
Roloff
-
Henry Beckman
William
-
Edward Andrews
Linus Farthing
-
William Hutt
Dr. Pete Marshall
-
Antoinette Bower
Dr. Heather Marshall
-
Ivor Barry
Chief Rathe Masters
-
Doug McGrath
Sergeant
- Vivian Reis Jane
- Clive Endersby 1st Tube Dweller
- Alan Bleviss 2nd Tube Dweller
- Carol Lazare Teale
-
Diana Barrington
Janice
- Ted Beatie Old Man
- Lillian Graham Old Woman
- Gina Dick Supervisor
- Michael Tough #2
- Ricky O'Neill #6
- Mark Lynas #7
- Trudy Young Lethe
- Iréna Mayeska Dr. Diana Tabor
- Tim Whelan Village Elder
- John Bethune Villager "A"
-
Nerene Virgin
Valerie
- Calvin Butler Cort
-
Allen Stewart-Coates
Magnus (voice)
- William Clune Captain
- Danny Hodgkins Monster
- Pat Galloway Trent
-
Doris Petrie
Nurse
- Patty Elsasser Secretary
- Les Rubie City Man
