How do you learn from the past if there isn't one?

Sixty years ago, something awful happened. Something that killed everyone except the people at Blue Ring. Something that caused the Headmasters to appear. But Maple doesn't know what it was. Because talking about the past is forbidden.

Everyone at Blue Ring has a Headmaster. They sink their sinewy coils into your skull and control you, using your body for backbreaking toil and your mind to communicate with each other. When someone dies, their Headmaster transfers to someone new. But so do the dead person's memories, and if one of those memories surfaces in the new host's mind, their brain breaks. That's why talking about the past is forbidden.

Maple hates this world where the past can't exist and the future promises only more suffering. And she hates the Headmasters for making it that way. But she doesn't know how to fight them - until memories start to surface in her mind from someone who long ago came close to defeating the Headmasters.

But whose memories are they? Why aren't they harming her? And how can she use them to defeat the Headmasters? Maple has to find the answers herself, unable to tell anyone what she's experiencing or planning--not even Thorn, the young man she's falling in love with. Thorn, who has some forbidden secrets of his own . . .