It’s 1981, and thirteen-year-old Roscoe McAdams and his brother and sister have always lived with their parents, Sebastian and Moonstar, in an isolated cabin high on a ridge in California’s northern Sierra, though often in spring when Moonstar can’t stand the snow anymore she takes them for a stay down below. They’ve mostly been home-schooled.

Then, through a fluke that April, Moonstar becomes a substitute teacher in a small town and enrolls the kids in school there. Roscoe assumes that when summer comes, they’ll go back to the ridge and Sebastian: that’s how it’s always been. But they don’t, and then everything Roscoe thinks he knows for sure begins to fall apart.