When Cora Mason wakes in a desert, she doesn't know where she is or who put her there. As she explores, she finds an impossible mix of environments - tundra next to desert, farm next to jungle - and a strangely empty town cobbled together from different cultures and time periods, all watched over by eerie black windows. And she isn't alone.

Four other teenagers have also been taken: a beautiful model, a tattooed smuggler, a secretive genius, and an army brat who seems to know too much about Cora's past. None of them has a clue as to what happened, and all of them have secrets. As the unlikely group struggles for leadership, they slowly start to trust each other. But when their mysterious jailer appears - a handsome young guard called Cassian - they realize that their captivity is more terrifying than they could ever imagine: Their abductors aren't from Earth. And they have taken the five teenagers to an otherworldly zoo - where the exhibits are humans.

When a forbidden attraction develops between Cora and Cassian, she realizes that her best chance of escape might be in the arms of her own jailer - though that would mean leaving the others behind. Can Cora manage to save herself and her companions? And if so...what world lies beyond the walls of their cage?