The Sinister Sign Post (later retitled The Sinister Signpost) is the fifteenth volume in the original The Hardy Boys series of mystery books for children and teens published by Grosset & Dunlap.
This book was written for the Stratemeyer Syndicate by Leslie McFarlane in 1936. 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 1968 by Tom Mulvey