Eight months ago, during the snowy depths of winter, strangers Alaric and Naia Underwood unwittingly switched realities. When they met again in June, floodwaters were raging all around them, and tragedy struck, altering both of their lives forever.

It's fall now, and Naia feels that something—or someone—is haunting her. Caught in yet another reality, she witnesses things that don't make sense, frightening things, including an Alaric who lives in the forest like a savage. But here, she hopes, she will find the answers to so many questions—if she can only reach the man who calls himself Aldous U.

But what will be her fate—and that of all the Underwoods—if she can't?