Derek Farr

as Ivan Mason / Dr. James Paxton

Ella Raines

as Rhona Ellison

Donald Wolfit

as Prof. Cattrell

Lisa Daniely

as Nurse Mitzi

Bruce Beeby

as Dr. Manning

Russell Napier

as Scotland Yard Supt. Davidson

Cyril Cusack

as Dr. Kelly

Frederick Piper

as Medwood Inspector Hayman

Karl Stepanek

as Dmitri Balinkev

Alfred Maron

as Ambulance Driver

John Welsh

as George White - the Gamekeeper

Olive Sloane

as Mrs. Lemmin - the Landlady