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. 　　译文(3): 在第一次世界大战的末期；神秘船；拖着一艘潜艇驶向西班牙海岸。他们的任务是找到并击沉一艘在打击盟军航运方面特别有效的U型潜艇。这艘神秘船伪装成一艘无害的纵帆船，实际上配备了一门能击沉U型潜艇的强大火炮。在加那利群岛停下来加油，船员们与当地人以及德国人进行互动，其中包括U艇指挥官的妹妹，她潜伏在海上等待即将到来的战斗。