Cass' work as a memory catcher makes the world a better place, while her enemies - the memory stealers - spread evil. Now, she faces a competition that will bring her face to face with the enemy, and if she loses, her city and those she loves will be done for. The problem is, her powers to copy and transmit memories are waning. Guided by disturbing dreams and a stranger who helps her to see an unfamiliar past, Cass discovers the reason for her weakening powers - and the danger she must face if she hopes to get them back.