Dana Andrews as Dr. John Holden

Peggy Cummins as Joanna Harrington

Niall MacGinnis as Dr. Julian Karswell

Maurice Denham as Professor Henry Harrington

Athene Seyler as Mrs. Karswell

Liam Redmond as Professor Mark O'Brien

Reginald Beckwith as Mr. Meek

Ewan Roberts as Lloyd Williamson

Peter Elliott as Professor K.T. Kumar

Rosamund Greenwood as Mrs. Meek

Brian Wilde as Rand Hobart

Richard Leech as Inspector Mottrarn

Lloyd Lamble as Detective Simmons

Peter Hobbes as Superintendent

Charles Lloyd Pack as Chemist

John Salew as Librarian

Janet Barrow as Mrs. Hobart

Percy Herbert as Farmer

Lynn Tracy as Air Hostess

John Harvey as Hobart's Brother

Alan Beaton as

Hyma Beckley as

Ballard Berkeley as

Ernest Blyth as

Wallace Bosco as

Daniel Brown as

Jimmy Cains as

George Curtis as

Richard Duke as

Shay Gorman as

Laurence Hepworth as

Walter Horsbrugh as

Arthur Howell as

Anthony John as

Dan Lester as

Leonard Llewellyn as

Michael Peake as

Paul Phillips as

Anthony Richmond as

Peggy Scott Sanders as

Terry Sartain as

Leonard Sharp as

Bert Simms as

Robert Brooks Turner as