Lewis Trilogy. Book 3. The Chessmen

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 and Fin puts together the fractured pieces of the past, he realizes that revealing the truth could destroy the future.