In the waning days of WWI, a U.S. "Mystery Ship," sets sail for the coast of Spain towing a submarine. Their mission is to find and sink a U-boat that has been especially effective in attacking Allied shipping. Posing as a harmless schooner, the mystery ship is in fact fitted with a formidable gun capable of sinking a U-boat. Stopping in the Canary Islands to refuel, the crew interacts with locals involved with Germans, and with Germans themselves, including the sister of the U-Boat commander, who is lurking offshore waiting for the coming battle.
George O'Brien
Marion Lessing
Mona Maris
Walter C. Kelly
Warren Hymer
Steve Pendleton
Walter McGrail
Larry Kent
Henry Victor
John Loder
Philip Ahlm
Al Bennett
Earl Wayland Bowman
Bill Brande
William Collier Sr.
Leonard Davison
Joseph Depew
Francis Ford
Robert Ford
Hans Fuerberg
Curt Furberg
Al Generaux
Bob Gillette
George Golden
Ben Hall
George Harris
Bob Kyle
Jack Martin
Harry Mount
Jack Murphy
Maurice Murphy
Bob Nelson
Edward Peil Jr.
Nat Pendleton
Terrance Ray
Marvin Schecter
Harry Schultz
Ferdinand Schumann-Heink
Robert Shepherd
Harry Strang
Anton Tell
George Templeton
Harry Tenbrook
T.J.F. von Blankerburg
Frank Walton
Harry Weil
Hans Winterhalder