Polly Greene has always been considered strange, a girl who can see a person's true colors, a thirteen-year-old more comfortable foraging in the woods with her eccentric grandmother than hanging out with friends. But all that is about to change when Polly's older sister, Bree, vanishes into the woods. The only one who believes Bree can survive, Polly begins to leave food in the woods for her sister and finds a hidden grove she names Girlwood, where she believes Bree is burning a fire each night. Along with an odd but endearing group of friends, Polly clings to the hope that she can see her sister through the harsh, snowy winter. And, in the process, she discovers the cruelty, bounty, and magic of the woods. Will Polly save her sister? And even if she does, will Girlwood survive?