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Louis Hayward

Philip 'Scotty' Grayson

Dennis O'Keefe

Daniel F. O'Hara

Louise Allbritton

Dr. Anastasia 'Toni' Neva

Carl Esmond

Dr. Ritter von Stolb

Onslow Stevens

Igor Braun

Raymond Burr

Krebs

Art Baker

Dr. Frederick Townsend

Lowell Gilmore

Dr. William Forrest

Philip Van Zandt

Anton Radchek

Charles Evans

Dr. Homer Allen

Frank Ferguson

Carl Bemish

Reed Hadley

Narrator (voice)

Ray Teal

Police Sergeant

William Tannen

FBI Chemist

Gale Storm

Voice on Tape Recorder

Arthur Space

Mr. North