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

Tamara Shayne

Mrs. Ecko, the Landlady

Keith Richards

FBI Agent Miller

Grandon Rhodes

Adolph Mizner

Steve Pendleton

Police Detective Gaines

Howard Negley

Feodore

Jimmy Lloyd

FBI Agent Alison

Myron Healey

FBI Agent Thompson

John Hamilton

G.W. Hunter

Paul Bryar

Fred Coby

Bert Davidson

Marten Lamont

Lee Phelps

Suzanne Ridgway

Arthur Tovey

Crane Whitley