Carry On follows the lives of Simon Snow, Bax, Agatha and Penelope at the Watfords School of Magicks. Simon, the main character, is called the "Chosen One" but is jokingly known as the worst "chosen one." His character is that of an awkward, lovable teenager with immense responsibility. He must balance his studies with romantic love interests and monsters. His girlfriend, Agatha, dumps him in search of a partner who can provide her with more prestige. Simon is left questioning his sexuality when Baz re-enters his life. Baz is his roommate and a member of the Pitch family as well as a vampire. Baz's mother was the former headmistress of the Watfords School of Magicks. She was killed in a vampire attack on school grounds. This is when Baz was turned into a vampire. At the start of the novel Baz is captured by numptys and held captive in a coffin. While he is away, the ghost of his mother returns to his room. Simon is the only one there and she asks him to avenge her murder. Simon agrees to relay the message. Baz is set free by his aunt and returns to the school. Simon's annoyance and frustration is matched with an intense attraction to Baz. The two kiss and their dangerous romance ensues. Simon agrees to avenge Baz's mother's murder with him. The two embark on a monster-filled adventure.