Mrs. Sally Jordan asks her faithful former houseboy, Charlie Chan, who is now a detective on the Honolulu police, to personally transport an extremely valuable pearl necklace from Honolulu to San Francisco that she has agreed to sell to millionaire P. J. Madden through jewelry broker and family friend, Alexander Crawford. Following the completed sale of the pearls, an adamant Madden states, “I want them delivered to my offices in New York and nowhere else.”
However, when Crawford learns that his son, Bob, had been followed by suspicious characters, and when the elder Crawford receives conflicting instructions Madden to have the pearls brought to his house near the desert town of El Dorado, he becomes suspicious. It is decided that Bob will precede Chan at the millionaire’s desert home to make sure that the place is safe. “Blind man feels ahead with cane before proceeding,” says the detective, as Bob adds, “And I’m the one to be the cane, right?”
On the train to El Dorado, Bob meets Paula Graham, a film director’s assistant who is traveling to the same town to arrange a film shoot on Madden’s property. As they approach the ranch by a hired car, driven by a local character named Will Holley, they hear two gunshots, and as they near the house, a figure is seen running off.
At the house, Bob and Paula are coldly received by Madden’s assistant, Martin Thorne, who expresses surprise that Bob has arrived a day earlier than expected. When asked about the gunfire, Thorne suggests that someone in the desert was probably “taking pot shots at jack-rabbits.” Bob and Paula are told that Madden is away, while Thorne invites Bob to stay, as Bob has revealed that the pearls will arrive by messenger the next day.
The following day, Chan arrives, and to Bob’s surprise, he is dressed as a menial, speaking in sing-song broken English, and calling himself “Ah Kim.” As the regular cook is away on family matters, Thorne decides, with a well-planted suggestion by Bob, to hire Ah Kim.
With the run of the house, Chan begins to search for clues and notices a revolver from Madden’s collection that is mounted on a wall has been removed and used recently. In Madden’s bedroom, he finds a bullet hole in the wall that has been hastily covered by a painting, and blood stains on the carpet, which someone has also tried to conceal. “Second bullet reposing in victim,” states Chan. Bob believes that Thorne has murdered Madden, which Chan believes might be a possibility.
Bob and Chan are somewhat shocked when Madden shows up later that day, driven to the house by Thorne. Bob suggests to Chan that, even though the situation is suspicious, they have no choice but to deliver the pearls to Madden as planned. Chan states that certain things should be cleared up before the pearls are handed over, and that Madden should be stalled.
Agreeing to follow Chan’s idea, Bob continues to put off the delivery of the necklace, finally convincing Madden that the pearls will be delivered on Sunday, two days hence. As Bob leaves a fuming Madden, he suddenly hears a voice crying, “MURDER!” As everyone runs to the source of the screams, Bob is surprised to find that it is a talking parrot. During its dialog, the parrot speaks a phrase in Chinese, to which Chan, in the guise of Ah Kim, replies to the bird. The next day, the “Chinese parrot” is found dead by Chan, who finds that someone used poison to do away with him. Chan feels that the bird had been repeating things that were said during the murder at the house, and that someone had now killed the parrot to stop anyone from hearing them repeated.
Later that day, Professor Gamble, apparently an old friend of Madden’s, arrives at the ranch. Gamble, Thorne, and Madden then drive into town, leaving Chan and Bob alone at the house. The two men continue their search for clues, turning up more useful information, including some belongings of someone named Jerry Delaney. However, the mystery is far from solved, as Chan and Bob reach no concrete conclusion, except for the possibility that Delaney may have been the murder victim.
Chan later heads into the desert, following clues that lead him to the man who had been seen by Bob running away after the gunfire during his arrival at Madden’s house on the first night. The detective learns from this person, an old prospector named Hewitt, who had witnessed the shooting while peering through a window, that it was actually Madden who had shot some unseen person.
Meanwhile, Bob is in El Dorado sending a telegram to his father. As he prepares to return to Madden’s house, he sees Madden’s cook, Louie Wong, who has just gotten off of the train, and gives him a lift back to the ranch. As they arrive, Bob sees Chan at the garage and leaves Louie to talk with him. As both men return to the car, they find that Louie has been killed with a knife. When Constable Brackett is called to the scene, he immediately suspects that Ah Kim (Chan) has killed Louie in order to keep his job as cook. However, Bob, protecting Chan’s guise as Ah Kim, firmly declares that he was with Chan when Louie was murdered, and Brackett leaves, still unconvinced.
On Sunday, the movie crew arrives at Madden’s house to do its shooting. During the filming, the director asks Paula to investigate an old abandoned mine in the hills as a possible location site for the next film. When Paula fails to return, Bob has Will Holley drive him up to the abandoned mine. At the mine, Bob calls out to Paula, who calls back. Suddenly Bob and Holley are captured by one of the men who had tailed Crawford back in San Francisco. With a quick move, Bob surprises the crook, named Maydorf, and after a struggle, overcomes him. Reaching Paula, who had been held prisoner, Bob is told that there is another captive being held.
Meanwhile, at the Madden ranch as evening falls, Sally Jordan’s son, Victor, arrives and ruins Chan’s investigation by informing Madden that the detective has had possession of the pearl necklace the whole time he was at the house, and that they should have been handed over days ago. Demanding that Chan hand over the pearls, and showing the detective a note from his mother instructing him to do so, Chan reluctantly complies with Victor’s wishes while requesting a signed receipt from Madden.
When Madden signs the receipt with his left hand, Chan quickly grabs the necklace and pulls a gun, knowing that the real Madden is right-handed. Brackett suddenly arrives on the scene and, believing that Chan is in the process of robbing Madden, fails to pay any heed to Chan’s protests to the contrary. Just as Chan is forced to hand the pearls back, the real Madden, with his arm in a sling and dried bloodstains on the shoulder of his shirt, suddenly walks in with Bob, Paula, and Holley, who has a gun in Maydorf’s ribs.
After a quick struggle, the false Madden, who is a look-alike and actor named Jerry Delaney, and who had attempted to impersonate Madden years earlier as part of a racket in New York, is subdued. Madden then rightly accuses Thorne of having double-crossed him. As he tries to slip away, Chan stops professor Gamble, revealing that, hidden on his person is the knife that was used to kill Louie Wong.
With the case solved, and the pearls safely in the hands of their new owner, Chan, Bob, and Paula take the train out of El Dorado. On the rear platform, Paula and Bob are seen embracing as the train leaves.