Good Blood — Aaron Elkins

Soaking up the sun on their friend's idyllic island in Lake Maggiore, Gideon and his wife soon learn that the breathtaking view and sumptuous food come at a price. The padrone's only child has been kidnapped. And when nearby construction workers unearth human bones, Gideon agrees to identify them -- exposing some extraordinary deceptions at the dark heart of a highborn family...