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The Unseen Enemy in this wartime meller is Nick (Leo Carrillo), the outwardly effusive manager of a San Francisco waterfront café. To make enough money to ensure his daughter Gen's (Irene Hervey) entree into society, Nick sells his services to a gang of foreign spies, who then use Nick's establishment as a rendezvous point. The plan is to covertly send out a Japanese vessel for the purpose of raiding and destroying American merchant ships. The spies' secret code is hidden in the lyrics of a song called "Lydia", which the unwitting Gen performs on request day after day. When our heroine finally figures out that something is amiss, she teams with government agent Sam (Andy Devine!) to foil the bad guys. Nick finally redeems himself in the final footage, inevitably at the cost of his own life. In an unusual move for 1942, all the cast and production credits for Unseen Enemy were reeled off at the end of the picture, rather than the beginning.