The Witch Twins are neither witches nor twins. In the eyes of their peers, however, the inseparable pair are equally strange: fiery Ronnie's dreams have a tendency to come true, and Malcolm is too cold and clever to connect with anyone else. Bound together by fate and friendship, they've spent ten years protecting one another from parents, cruel teens, and the mysterious Hunters that Ronnie knows will come for Malcolm eventually. In the summer after high school graduation, however, Ronnie is troubled by a new dream. It tells her that things are about to change, and their friendship will not be enough to protect them from the encroaching threats. They need a warrior.

Aiden Newcastle is young to be an ex-soldier with tinnitus and a drinking problem. When he gets into a fight protecting the Witch Twins at a local dive, he begins to remember what made him a soldier in the first place: a relentless sense of honor and a desire to help others. While the pair aren't exactly helpless, he knows that they won't survive whatever is coming without his strength. He can't let himself worry about whatever else they—or he—might want.

Together, Ronnie, Malcolm, and Aiden must face thinking machines, unsettling portents, hungry strangers, their own government, and an impossible truth. If they survive it all, the question will still remain: who are they to one another?