The Secret of the Lost Tunnel

Blurb

The Secret of the Lost Tunnel is Volume 29 in the original The Hardy Boys Mystery Stories published by Grosset & Dunlap.
This book was written for the Stratemeyer Syndicate by Andrew E. Svenson in 1950. 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 shortened in 1968 resulting in two different stories with the same title.