This is Why We Lied by Karin Slaughter (Part of the Will Trent series)

 Boy, this story really makes you appreciate growing up in a loving, supportive family. Will and Sara are on their honeymoon at the isolated McAlpine Mountain Lodge. Their first night there, Mercy, the daughter of the family that owns the lodge, screams for help--then dies in Will's arms out in the woods. Her last words were for her teenage son, Jon. Will calls in his boss Amanda and partner Faith because he doesn't have a lot of faith in the abilities of the local law.  

The more he and Faith investigate, the more they realize that this family had lots of nasty secrets, that Mercy was pretty much trapped in a miserable existence on the mountain, and that there is more than just murder going on. The more the story unravels, the murkier and more depressing it gets. Making things particularly uncomfortable for Will is the existence of the family's adopted son, Dave, who had been in foster care with Will--and christened him with the name Trashcan.