In an unnamed land in the not-so-distant future, Grace is raised to be an Angel, a suicide bomber trained to die for the freedom of her rebel society. But Grace refuses to die for the cause. And now she's on the run - but she isn't alone. Kerr, who has a dark past of his own, is accompanying Grace on her cross-country train ride. As Grace struggles to hide her secret, the fear of discovery looms large as she recalls the series of events that brought her to that train and her uncertain fate.