Charlie Chan travels from his home in Honolulu to Reno to solve the murder at the request of Mary's soon-to-be ex-husband.
On arrival in Reno, Chan spars pleasantly with Sheriff Tombstone Fletcher, an old-timer who isn't up-to-date on modern police methods.
Driving to Reno to meet his father, he picks up some "friendly" hitch-hikers who steal his car, strip him to his underwear, and abandon him in the middle of nowhere.
Charlie exposes the murderer by revealing an acid burn on the arm that had been hidden by unfashionably long sleeves.
Chan also exposes the "respectable" Dr. Ainsley as a fortune hunter who had sought to poison one of his female patients for inheritance money.