Charlie Chan in Honolulu

When murder is committed on the good ship Susan B Jennings, Charlie has just left home. Young son Tommy takes the phone call when Charlie is assigned the case and persuades elder brother Jimmy (who wants to be a detective) to accept the assignment. Jimmy goes out to the ship himself (secretly followed by Tommy), where he's mistaken for his father as he proceeds to examine the case. Charlie finally finds out and rushes to the harbor where he straightens things out and begins to investigate. Among the suspects is a doctor who keeps a living human brain in a suitcase in order to continue experiments on it, a police detective who is taking in a prisoner and seems keenly interested in Chan's case, and a nervous fellow who nevertheless is escorting a pet lion. $300,000 gets stolen, another passenger is murdered, and the Captain of the freighter is putting pressure on the Honolulu Police Department to let him take the ship out of the harbor and precede on its way before the shipping company loses too much money.