Download or read book Hardy Boys 15: The Sinister Signpost written by Franklin W. Dixon and published by Penguin. This book was released on 1936-09-01 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: In one of the most dangerous and intriguing cases of their careers, Frank and Joe Hardy help their father investigate a series of mysterious car accidents. Each of the drivers had seen a signpost marked DANGER shortly before his accident. The young detectives investigate, only to discover that the signposts have vanished. The attempted theft of a secret experimental motor and the kidnapping of a famous race horse are part of this thrilling case, which proves to be as sinister as the signposts themselves.