After a plague turns most of the human race into zombies, a barrier separating the remaining humans and zombies. The zombies walk through life without meaning, after giving up the urge to go on, zombies rip off their skin (act that accelerates the Bonification process) and become Boneys.
In the novel, Boneys are the dominant faction of the undead: Zombies are called 'Fleshies' and are in submissive status.
As their name suggests, they appear to be nothing but walking skeletons, they'll attack and eat anything with a heart beat, though the zombies do too, they're conflicted about it. Though they don't speak, they have thoughts and hunt in packs. In spite of their skeletal appearance, Boneys are not only just as dangerous as zombies, some of their physical attributes are even enhanced such as speed, wall crawling etc. They also possess advanced cunning when they ambush human soldiers, establish statuses (such as Elders), officiating marriage between zombies, sharing pictures of battles they had against humans in an attempt to establish trusts, camaraderie and strengthen their social position.
The focus of Warm Bodies is about a zombie named R that falls in love with a human named Julie. R brings Julie back with him and protects her, and eventfully helps her return to her father Colonel Grigio, the zombie hating leader of the human resistance. Julie's impact in R's life results in him slowly becoming human again. The feeling of emotion spreads and the zombies begin curing themselves.
The Boneys, fearing their extinction, runs the healing zombies away and begin hunting R and Julie down, plotting to zombies fend them off, allowing R and Julie to escape. But the Boneys' numbers prove too great and they find R and kill them. The Boneys form a massive army, and attack the barrier. The Boneys find R and Julie, but the now healing Julie and trap them. Desperate, the two lovers jump out a building into a pool, R shielding Julie. When the two survive the fall, Julie kisses R, and the kiss results in him becoming fully human again. But Colonel Grigio arrives and shoots R, thinking he is attacking her, but the colonel and his soldiers see R bleeding, proving he is human and the zombies are healing themselves. Colonel Grigio orders the soldiers not to kill zombies, but the Boneys, with the combined forces, the humans and zombies defeat the Boneys, leading to the Boneys' weakening and eventual downfall and a peace between zombies and humans.
They ultimately surrendered themselves to humanity in the novel's epilogue. In the end, like living humans with having a lot, Boneys were afraid to be changed.