Big Sky by Atkinson Kate

Jackson Brodie has relocated to a quiet seaside village, in the occasional company of his recalcitrant teenage son and an aging Labrador, both at the discretion of his ex-partner Julia. It’s picturesque, but there’s something darker lurking behind the scenes.

Jackson’s current job, gathering proof of an unfaithful husband for his suspicious wife, is fairly standard-issue, but a chance encounter with a desperate man on a crumbling cliff leads him into a sinister network — and back across the path of his old friend Reggie. Old secrets and new lies intersect in this breathtaking novel by one of the most dazzling and surprising writers at work today.