Plot summary

The story begins with Frank and Joe Hardy barely avoiding being hit by a speeding driver whom they notice has bright red hair. Later, this same red-haired driver attempts a ferryboat ticket office robbery and successfully steals a yellow jalopy called Queen from the Hardys' friend, Chet Morton. Due to one witness reporting that the villain had dark hair, the Hardys assume he is using a red wig. It is learned that the thief returned to Chet's home to steal a tire, helping Frank and Joe to find Queen abandoned in a public wooded area.

The excitement of finding Queen is quickly gone when it is reported that there has been a robbery of forty thousand dollars in securities and jewels from the Tower Mansion owned by siblings Hurd and Adelia Applegate. Hurd Applegate is convinced that the Tower's caretaker, Henry Robinson, is the guilty party. The Hardys are especially concerned by this accusation because Henry's son, Perry, is a friend of theirs who will have to quit school to work since his father can no longer get a job as a result of Applegate's accusation. The only 'proof' of Henry Robinson's guilt is that he was suddenly able to pay off a debt, and refused to reveal where he got the money to pay off the debt.

The Hardys suspect that the red-haired man may be involved with the Tower robbery and search the place where The Queen was found, finding the red wig. The Hardys' dad, detective Fenton Hardy, learns that the wig was manufactured in New York City. The three Hardys go to New York and learn of a criminal named John "Red" Jackley who is fond of using disguises. Soon, Jackley is injured in a railroad handcar accident causing him to be hospitalized. About to die, Jackley confesses that he committed the Tower Mansion robbery and put the loot "in the old tower…" Jackley dies before he is able to explain further. After searches inside and outside of the Tower Mansion the stolen loot is still not found.

Frank and Joe decide to go to the railroad where Jackley used to work to find out more information. While investigating, they see two water towers nearby. The Hardys realize that Jackley was referring to the old water tower and not the Tower Mansion. Inside the water tower they find the stolen items but are locked in the tower by a man calling himself Hobo Johnny. Johnny feels that anything in the tower belongs to him. Frank and Joe broke out of the water tower and return the securities and jewelry. Then they are rewarded a thousand dollars for returning the missing jewels. In the original version of the book Henry admits that a man who owed him money repaid a debt to him, but he was not allowed to tell anyone in case the man's other debtors found out. This was revised in the 1959 version such that Adelia reveals that she loaned Henry Robinson the money to pay off his debt. Following the revelations and with the stolen loot returned, Hurd re-hires Henry with an increase in salary and Hurd builds the greenhouse that Henry has been wanting.

Original edition (1927)

• Ghostwriter: Leslie McFarlane
• Summary: The Tower Mansion has been robbed and the father of a friend is under suspicion. The boys discover the real thief and track down the loot.

Revised edition (1959)

• Revision type: Completely rewritten, but follows same basic plot.
• Ghostwriter: Harriet S. Adams