The Secret of the Old Mill

The Secret of the Old Mill

Original 1927 edition
Author	Franklin W. Dixon
Country	United States
Language	English
Series	The Hardy Boys
Genre	Children's literature/Young adult literature
Publisher	Grosset & Dunlap
Publication date	June 1, 1927, revised edition 1962
Pages	original edition 212, revised edition 174
OCLC	1718891
Preceded by	The House on the Cliff
Followed by	The Missing Chums

The Secret of the Old Mill is Volume 3 in the original The Hardy Boys Mystery Stories published by Grosset & Dunlap. The book ranks 86th on Publishers Weekly's All-Time Bestselling Children's Book List for the United States, with 1,467,645 copies sold by 2001. This book is one of the "Original 10", some of the best examples of the Hardy Boys, and Stratemeyer Syndicate, writing.

This book was written for the Stratemeyer Syndicate by Leslie McFarlane in 1927. Between 1959 and 1973 the first 38 volumes of this series were systematically revised as part of a project directed by Harriet Adams, Edward Stratemeyer's daughter. The original version of this book was rewritten in 1962 by Alistair Hunter resulting in two different stories with the same title.

The Hardy boys learn a case of counterfeit money is somehow intertwined with a national security case their dad is working on.

Frank and Joe help prevent 14-year-old cyclist Ken Blake from getting killed in an accident. As they help the boy up they see he is delivering an envelope to Victor Peters, a name that means something to the Hardys later on in the book.

The Hardys learn that their friend Chet Morton has been tricked when asked to make change for what turned out to be a counterfeit twenty dollar bill, something that the police later confirm is becoming more common in their town of Bayport.

Later, Joe is awakened by a clattering sound and sees a mysterious figure bicycling away from the Hardys' home. While investigating the disturbance a note is found that reads, "Drop case or else danger for you and your family." The Hardy boys are not sure if this threat refers to the counterfeiting case that Frank and Joe are investigating or another case their detective dad, Fenton Hardy, is trying to solve.

The Hardys go with Chet, who wants to apply for a job at Elekton Controls, a missile-development company, but are told by Mr. Markel, one of Elekton's security guards, that there are no openings. Before leaving, they notice a bike that looks similar to the one ridden by Ken Blake and that is likely to have been used by the person who left the threatening note. Mr. Docker, an Elekton maintenance man, tells them that Ken does odd jobs for the company, but that he is not there at that time, even though Joe is certain he saw Ken looking out an adjacent old watermill's window at them. The Hardys, their girlfriends, Iola Morton and Callie Shaw and Chet go nearby to have a picnic but an arrow is shot at them with an attached note reading, "Danger. Hardys beware."