Cassi loves spending time with her grandfather. His games, songs, and stories have always brought her endless joy. This visit with him, though, is different: Grandpa seems to be losing track of things, including everything from the stories they're sharing to who Cassi herself is. So when he goes missing after wandering off from his own backyard, Cassi knows she has to figure out where he's gone.

What she discovers is a world filled with memories, none of them her own. As she leaps from one memory to the next, she knows she's getting closer and closer to finding her grandfather--but only if she can make sure he doesn't slip away forever.