Characters played by Dana Andrews
John Holden
Characters played by Peggy Cummins
Joanna Harrington
Characters played by Niall MacGinnis
Doctor Julian Karswell
Characters played by Maurice Denham
Professor Henry Harrington
Characters played by Athene Seyler
Mrs. Karswell
Characters played by Liam Redmond
Mark O'Brien
Characters played by Reginald Beckwith
Mr. Meek
Characters played by Ewan Roberts
Lloyd Williamson
Characters played by Peter Elliott
Kumar
Characters played by Rosamund Greenwood
Mrs. Meek
Characters played by Brian Wilde
Rand Hobart
Characters played by Richard Leech
Inspector Mottram
Characters played by Lloyd Lamble
Detective Simmons
Characters played by Peter Hobbes
Superintendent
Characters played by Charles Lloyd Pack
Chemist (as Charles Lloyd-Pack)