What Happened at Midnight
| Publisher | Grosset & Dunlap |
| Publisher Series | Hardy Boys Mystery Stories |
| Series | The Hardy Boys |
| Format | Hardback |
| Language | English |
| Location | New York |
| Copyright | 1967 |
| Pages / Font | 173 pages |
| Series Number | 10 |
| ISBN | 0-448-08910-6 |
| Library of Congress Classification Number | 67-10522 |
Added by jlkrien · Last edited by miketaylor81