Puffin The Whispering Mountain (Prequel to the Wolves Chronicles series)

In the small town of Pennygaff, the legendary Harp of Teirtu is found - and lost again. For young Owen Hughes and his friend Arabis, it is the start of a hair-raising race to save the harp from sinister Lord Malyn. As they struggle to keep it out of his hands, they are plunged into a wild adventure involving murder, kidnapping, underground worlds, savage beasts, floods, avalanche, the mysterious children of the Pit - and above all, a man who will stop at nothing to get the harp back again. Winner of the 1969 Guardian Fiction Award.