Four explorers are summoned to Peru by the brilliant physicist Dr Thorkel. They discover a rich source of radium and a half-mad Thorkel who shrinks them down to one-fifth their normal size when they threaten to stop his unorthodox experimentation.
as Dr. Alexander Thorkel
as Bill Stockton
as Dr. Mary Robinson
as Dr. Rupert Bulfinch
as Steve Baker
as Pedro
as Dr. Mendoza
as Prof. Kendall
as Woman (uncredited)
as Silent Indian (uncredited)
