A mad scientist uses captured criminals as experiments for his study on "the criminal mind" aboard his private ship.

Lyle Talbot
as Lt. Bob Bennett

Irving Pichel
as Dr. Herbert Stander

Julie Bishop
as Joan Martel

Sheila Bromley
as Poison Mary Slavish

Anthony Averill
as Dirk - Stander's Aide

Russell Hopton
as Harry 'The Carver' Bogard

Julian Madison
as Paul - Stander's Aide

Eddie Holden
as Ole Olson

Wheeler Oakman
as John Ritter

Stanley Blystone
as Capt. Mike Briggs