While their father Fenton Hardy is working on case of museum robberies he asks Frank and Joe to stake out the Black Parrot, a shipping boat docked in Bayport. The Hardy boys get a job loading crates aboard the ship, but because the crew is so unfriendly and they are kept very busy, they don’t have a chance to investigate so instead they decide to follow another lead and travel to New York to search for a rare old book. While scouring a used book store they locate a book titled Empire of the Twisted Claw which bears a symbol on the cover which matches a ring the first mate of the Black Parrot was wearing.
Once again Frank and Joe Hardy accept the challenge of a puzzling case when their famous detective father asks the boys to assist him in tracking down a notorious jewel thief and his accomplices. The trail leads to the outskirts of the Hardy's home town and to a weirdly guarded mansion on the old Perth estate.
Frank and Joe solve the mystery of the secret locked room in the spooky Dalrymple Mansion. A banker named Ray Dalrymple of Lakeside gets death threats and shows up at the Hardy's house seeking Fenton Hardy's assistance. Frank & Joe offer to help, but at first he's reluctant. At last, he agrees. Soon after that, during a hike with their friends, the Hardy boys are nearly run over by a car, then investigate the Purdy place. After that, they rest and talk over their recent mis-adventures.
A plot to steal a top-secret instrument vital to the United States space program poses a challenging case to Frank and Joe Hardy. The whereabouts of their famous detective father is a mystery, so Frank and Joe are on their own to foil the plotters.
Frank and Joe Hardy, amateur detectives and brothers, investigate the mystery of a stolen boat and soon discover that the boat's disappearance is tied to a smuggling operation.
