The Green Man's Gift — Juliet E. McKenna

A teenage boy has turned up in Snowdonia, barely conscious and babbling about beautiful women and fairy feasts. The authorities blame magic mushrooms. The wise women say different and they want dryad's son, Daniel Mackmain, to investigate. He needs to watch his step in the mountains. Those who live in the hollow hills mask their secrets and intentions with sly half-truths.Far from the woods he knows, Dan needs help from the allies he has made in past adventures. But he's a loner at heart. As the true power of his adversary becomes clear, he must decide if he's willing to see those he cares for put themselves in danger.A modern fantasy rooted in the ancient myths and folklore of the British Isles.