Following their adventures in Yr Horwth and Melltith yn y Mynydd, the heroes of Copa Coch venture from their home for the first time, trailing the mystery that hides in the hills and marshes of the kingdom of Bryn Hir.
| ISBN: | 9781801060851 |
| Publication date: | 25th March 2022 |
| Author: | Elidir Jones |
| Illustrator: | Huw Aaron |
| Publisher: | Atebol |
| Format: | Paperback |
| Pagination: | 270 pages |
| Series: | Chwedlau'r Copa Coch |