Knife River by Justine Champine

When Jess was thirteen her mother went for a walk and never returned. Jess and her older sister Liz never found out what happened. Instead, they did what they hoped their mother would do: survive. As soon as she was old enough, Jess fled their small town of Knife River, wandering from girlfriend to girlfriend like a ghost in her own life, aimless in her attempts to outrun grief and confusion. But one morning fifteen years later she gets the call she’s been bracing herself for: Her mother's