When Jack's P.E. coach pairs him up with Jay Perkins for the cross-country team, neither of them is happy about it. Jack is grieving the loss of Joseph, his foster brother, and adjusting to his role as big brother to Jupiter, Joseph’s orphaned daughter. Dealing with Jay Perkins—who was definitely no friend of Joseph’s—is the last thing he wants to do.

But as Jack's running grows stronger, so do his relationships with both Jay and Jupiter, and he starts to feel more like himself than he has since Joseph died. He's finding his stride . . . until Jupiter’s grandparents decide to claim her as their own, and suddenly Jack’s past and present smash together, threatening to dissolve both his newfound confidence and his friendships.