Mrs. Sally Jordan asks her faithful, former houseboy, Charlie Chan, now a detective with the Honolulu police force, to personally transport to El Dorado a pearl necklace that she has sold to millonaire J. P. Madden, as something seems suspicious in the transaction. Bob Crawford, son of the jewelry store owner who has set up the deal, precedes Chan to Madden's house to insure that the place is safe and, on the train, meets Paula Graham, a film director's assistant traveling to El Dorado to arrange a film shoot on Madden's property. As they approach the ranch by cab, they hear gunshots. Inside the house, Martin Thorne, Madden's secretary, bends over a body in the bedroom and, when he answers Paula and Bob's knock, tells them that Madden is away and urges Bob to stay, though Bob has revealed that the pearls will arrive the next day by messenger. Chan arrives the next day dressed as a menial, calling himself "Ah Kim," and Thorne hires him as the new cook, as the regular cook is away. While snooping around, Chan notices that a revolver from Madden's collection has been removed and used recently. In Madden's bedroom, he finds bullet holes in the wall and blood stains on the carpet, which someone had attempted to conceal. Believing Madden to have been murdered by Thorne, Bob is amazed when Jerry Delaney, whom he believes to be Madden, shows up. As Bob and Chan drive into the garage one night, they find the dead body of the former cook. The cook's talking Chinese parrot, who made comments suggestive of a murder, is then discovered poisoned, which reveals to Chan that both the cook and the bird witnessed something amiss. Delaney demands that the necklace be handed over, and privately Bob asks Chan for the goods, but Chan is not yet convinced that everything is as it should be and holds on to Mrs. Jordan's property. Chan and Bob discover a suitcase in the attic that belongs to Delaney and ascertain that he arrived by train the night before Bob's arrival. The movie crew finally arrives, and when the director asks Paula to investigate an old mine where he wants to shoot a scene, a crook jumps out and attacks her. Bob goes looking for Paula, discovers her at the mine and struggles with the crook before finally overpowering him. Paula tells Bob that there is another captive in the mine, Madden. Soon after, Victor Jordan, Sally Jordan's son, arrives at the Madden ranch and blows the whole investigation by telling Delaney that Bob should have handed over the pearls days earlier and demanding that Chan, or "Ah Kim," deliver the pearls as his mother instructed. Delaney uses his left hand to sign a receipt, and Chan, knowing Madden to be right-handed, grabs the pearls and pulls a gun on him. Sergeant Brackett arrives and doesn't believe that "Ah Kim" is really Chan; he gives the pearls back to Delaney, just as Madden enters with a bandaged shoulder. Madden reveals that Delaney, his look alike, has a history of impersonating him and accuses Thorne, rightly, of double-crossing him. The case solved and the pearls safely delivered, Paula, Bob and Chan travel back to San Francisco, and on the rear train platform, Paula and Bob embrace happily.