The Chessmen by Peter May

Fin Macleod, now head of security on a privately owned Lewis estate, is charged with investigating a spate of illegal game-hunting taking place on the island. This mission reunites him with Whistler Macaskill—a local poacher, Fin’s teenage intimate, and possessor of a long-buried secret. But when this reunion takes a violent, sinister turn, Fin realizes that revealing the truth could destroy the future.