Bela Lugosi as Rolf

Lionel Atwill as Dr. King

Leif Erickson as Laurie

Irene Hervey as Dr. Lynne Harper

Ralph Morgan as Kurt Ingston

Don Porter as Dick Baldwin

Nils Asther as Agor Singh

Fay Helm as Margaret Ingston

Frank Reicher as Dr. Timmons

Doris Lloyd as Sarah Judd

Francis Pierlot as Dr. Phipps

Robert Homans as Captain "Cap" Beggs

Janet Shaw as Millie Carson

Eddy Waller as Jeb Harmon

Cyril Delevanti as Torque