Walter C. Kelly

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.