When a landslide traps Kirstie inside Dead Man's Canyon with a herd of wild horses, she must find a way to help their injured leader, a stallion hurt by the falling rocks, and find her own way out.

Five years ago, Mira Bunting founded a guerrilla gardening group: Birnam Wood. An undeclared, unregulated, sometimes-criminal, sometimes-philanthropic gathering of friends, this activist collective plants crops wherever no one will notice: on the sides of roads, in forgotten parks, and neglected backyards. For years, the group has struggled to break even. Then Mira stumbles on an answer, a way to finally set the group up for the long term: a landslide...