Lan Ying Lin's father, an importer of Oriental antiques, is murdered by smugglers after he refuses to help them smuggle illegal aliens into San Francisco. Detective Kim Lee is assigned to the case and meets with Lan Ying and family friend Mrs. Mary Hunt the night of the murder. Lan Ying is distrustful of the policeman's ability to solve the case and decides to crack the smuggling ring herself. Because her father thought that a man named Otto Hartman living in the Central American town of Port O'Juan, is the head of the smugglers, Lan Ying travels there. After some investigation, Lan Ying locates Hartman and hires on at his nightclub as a dancer. She finds his business ledger and discovers that he is not the chief of the smugglers after all. Kim Lee also comes to Port O'Juan after working undercover for the captain of the smugglers' ship Jenny Hawk . He meets Hartman through the captain and recognizes Lan Ying in the club, where they manage to speak privately. She reveals the location of Hartman's ledger and agrees to sneak aboard the ship dressed as a man. Hartman finds Kim Lee with the book and they struggle, until one of the refugees shoots Hartman, which allows Kim Lee to board the ship with no problems. After they set sail, one of the immigrants discovers Lan Ying is a woman, and they all attack her. Kim Lee comes to her aid, but he is knocked unconscious and drops the ledger. The captain finds it and suspects Kim Lee and Lan Ying of being spies. When the smugglers' seaplane meets the ship, they tie up the couple and put them over the plane's bomb doors. The smugglers open the doors as they are flying over the ocean, but Kim Lee and Lan Ying cling to the inside, and they swim ashore when the plane eventually lands. Kim Lee and Lan Ying stumble upon Mrs. Hunt's estate and discover that she is the head of the smuggling ring. She holds them captive, but Kim Lee is able to phone the Federal police, and he escapes with the help of Kelly, Mrs. Hunt's honest chauffeur. After a gunfight between the smugglers and the police, Mrs. Hunt and her cohorts are arrested. Kim Lee proposes marriage to Lan Ying, and she accepts.