The Headmasters is a young adult science fiction novel set one hundred years in the future. The story is told from the main character, Maple's, point of view. Blue Ring, where Maple lives, is inhabited by Headmasters, a species of bug that arrived sixty years prior, after an event that wiped out all other human life on the planet. The headmasters are a parasitic species that attach to the back of their human host and control their actions. When a host dies, their headmaster is transferred to a new host. The headmaster carries the memories of all of its previous hosts, so talking about the past is forbidden because if an old memory is triggered in a new host, their brain breaks. The headmaster's control of its hosts is not complete.  For a few hours each day the parasite goes dormant, and the people are in control of their own actions.  During the hours of the "slackening," Maple discovers her inner strength and possibly the salvation of her community.