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.
- ISBN10 0448089157
- ISBN13 9780448089157
- Publish Date 1 September 1936
- Publish Status Active
- Publish Country US
- Publisher Penguin Putnam Inc
- Imprint Grosset & Dunlap Inc.,U.S.
- Format Hardcover
- Pages 192
- Language English
- URL https://penguinrandomhouse.com/books/isbn/9780448089157