Mary Young is an artist, though she hates making art. She much prefers working with her immortal roommate, Ethan Avedon, who scours his Colorado territory, hunting down the guilty and punishing them for their sins. This work is dangerous for a human, but Mary is a natural, and she finds Ethan's work fulfilling. She ignores her nightmares and insists on playing the Karma game with Ethan.

Soon the young lovers are too busy guarding over their city to realize they are the ones being hunted. A strange and powerful immortal wants Mary for his own, and as she uncovers her forgotten past, she must decide how to face her destiny — without losing herself and everything she loves.