Claire Forrest seeks her kidnapped scientist father, hidden somewhere on Mystery Island. He is held and forced to work on diabolical inventions by Captain Mephisto, a costumed villain.
Richard Bailey
as Lance Reardon
Linda Stirling
as Claire Forrest
Roy Barcroft
as Capt. Mephisto
Kenne Duncan
as Sidney Brand
Forrest Taylor
as Prof. William Forrest
Forbes Murray
as Prof. Harry Hargraves
Jack Ingram
as Edward Armstrong
Harry Strang
as Frederick "Fred" Braley
Ed Cassidy
as Paul Melton
Frank Alten
as John Raymond
Lane Chandler
as Police Insp. Reed
Russ Vincent
as Ruga
