Eight-year-old Jack West has a frightening neighbor: the mysterious Mr. Beegle, who is the spitting image of mR mILDEW, the villain from a novel written by Jack's late grandfather. Jack's meeting with Mr. Beegle starts a magical journey in which the death, and even life, of his grandfather comes into question. Fact and fiction become intertwined and, increasingly, the only thing that can be counted upon is the imminent end of the world.

When The Exclamation Point, an immortal hero of Lit City, is murdered fellow superheroes Plus and The Question Mark turn to the world's highest paid coroner to help track down the killer. Lit City soon finds itself under siege as this new power declares war on the supposedly immortal demigods of Lit City.