Four days before Christmas in Edwardian-era Toronto, Detective William Murdoch is called to investigate a daring train robbery. When witnesses insist the culprit exhibited superhuman abilities, Constable Crabtree realizes the robber bears a striking resemblance to the title character of his new graphic novel, Jumping Jack. As Station House No. 4 contends with a real-life Jumping Jack, Inspector Brackenreid orders the formation of a police choir, and Dr. Julia Ogden tries to help two orphans who mistake her for a fairytale heroine.