In August 1918, as the U.S. Mystery Ship No. 2 sails from Yorktown harbor, the commander, Lieutenant Robert Kingsley, U.S.N., tells his crew, the nature of their secret mission: they are to provoke a German U-boat, commandeered by Baron Ernst Von Steuben, who has built up a reputation as an ace destroyer of ships near Gilbraltor, to fire on them so that the U-boat will be drawn into firing range of the submarine the Mystery Ship has in tow. The crew composed of an untested university naval reserve unit and an experienced, crack gun team, are encouraged to practice a “panic drill,” during which they will act like a merchant crew that his been shelled, running around screaming in fright and abandoning ship, to fool the enemy. When one of the gun crew acts out a tale of past heroism for the younger reservists, he falls into the ocean, and as he flails about, Ensign Dick Cabot, scion of an upper-class family, rescues him. Cabot receives the congratulations of the older men, who previously were skeptical of the reservists’ abilities. They reach a port in the Canary Islands that Bob has learned is used for refueling U-boats. Although Bob issues orders prohibiting the drinking of hard liquor and the fraternization with women, the sailors immediately cavort with enticing Spanish women and accompany them to a bar. Bob is attracted to a beautiful blonde woman, who, unknown to him, is Anna Marie Von Steuben, the sister of the feared U-boat ace. After Anna Marie arranges to accompany German officers, including her sweetheart, Franz Schiller, on a trawler to visit her brother in his U-boat, Lolita, a Spanish singer and dancer, receives orders from Franz to get information about the Americans. As she performs in a cafe, Lolita flirts with Cabot, and after she leaves, Cabot follows to return her shawl. She entices the shy man to her room and gives him drugged wine. When he passes out, a German officer searches him and finds papers to confirm that he is an American officer. While he is unconscious, Lolita, uneasy about what she has done, kisses him. After Bob and Anna Marie walk together by the sea, Bob and the German officers recognize each other as enemy officers. Defiantly, they toast to their next meeting. The Americans return to their ship and set out despite failed efforts to locate Cabot. He revives in time to see them leave, and after he spies Lolita accepting money from the Germans for her services, he sneaks on their trawler as it heads to the U-boat. While Anna Marie greets her brother Ernst on the U-boat, Cabot sets fire to the trawler and hacks at a pump. When a German shoots and kills him, Franz reprimands the man. The officers then salute Cabot during his burial at sea. After the U-boat leaves, the leak on the trawler is discovered, and Anna Marie is saved in a lifeboat. Sometime later, the Americans find Cabot’s body. They then locate the lifeboat, and Bob is forced to detain Anna Marie for questioning in relation to Cabot’s death. She confesses that she is Von Steuben’s sister and taunts the Americans. When the U-boat shells the Mystery Ship, the men begin their “panic party,” and Anna Marie signals the U-boat to stay away. Bob orders a man to shoot her if she makes another move. When the U-boat refuses to come closer, Bob orders his sub to be cut free to fight the U-boat itself. As the U-boat shells the Mystery Ship again and the hold explodes in a fire, Bob and others rescue two men below. The U-boat then comes into range, and the Americans sink it. As German prisoners, including Franz and Von Steuben, are picked up to be sent to a detention camp, Bob tells Anna Marie that he’s lost the only thing he ever cared about. Anna Marie assures him he will never lose that, but refuses when he suggests that they get married immediately. She explains that her country and people are in trouble and that she wouldn’t be worth wanting if she abandoned them. She will not accept film taken of the two of them that Bob tries to give her, and says it will be a reason for her to come back. She then walks off with her arm around her brother as Bob watches. More on Wikipedia or Mubi
Watch Seas Beneath (1931)
