After his prior adventures, the Chosen One Simon Snow, now without magic, feels depressed and traumatized. Penny offers three tickets to America to embark on a new mission to save Agatha from a vampire conspiracy. So Simon, Penny, and Simon's vampiric love Baz take a vintage convertible across the American West. Along the way they encounter dragons, vampires, creatures, and a new magic that they know nothing about, but that threatens to destroy the world.