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.
| ISBN: | 9780448089157 |
| Publication date: | 1st September 1936 |
| Author: | Franklin W. Dixon |
| Publisher: | Grosset & Dunlap an imprint of Penguin Young Readers Group |
| Format: | Hardback |
| Pagination: | 192 pages |
| Series: | The Hardy Boys |