Anna Kellogg has always felt different. Growing up in Hartwood, New Jersey--where frequent disappearances are attributed to an urban-legend-like beast that dwells in the walled-in swamp at the center of town--can have that effect on people. But for Anna, it's more than that. Since she was a child, she's been plagued by episodes where she sees things others can't see. Feeling different is one thing, but actually being different is another. If it weren't for her best friend, Olivia, Anna's not sure where she'd fit in.
But any hopes of having a normal senior year come to a halt when Olivia is attacked in the woods, bitten, and left for dead by a whirling cyclone of claws, fur, and teeth. Though Olivia survives, a sinister entity makes it clear that the mark had been set on Anna...and the miss has set in motion a catastrophic shift that will change Anna and her friends' lives forever.