After a trip to the pet store, fourth-graders Sussy and Guy bring home a spotted lizard, and they name her Matylda (with a 'y' so it's all her own). With Guy leading the way, they feed her and give her an origin story fit for a warrior lizard. A few weeks later, on a simple bike ride, there is a terrible accident. As hard as it is, Sussy is sure she can hold on to Guy if she can find a way to love Matylda enough. Eventually Sussy must discover what it means to grieve and heal and hope and go on, for her own sake and Matylda's.