Jack Smith is the story’s detail-oriented, cautious, and loyal protagonist. The eight-year-old has dark brown hair and wears glasses. Throughout Osborne’s series, Jack demonstrates his powers of observation and his love of knowledge by taking careful notes during his adventures with his sister. He records the Christmas Knight’s rhymes in his notebook, allowing him and Annie to gather clues about the obstacles they face in the Otherworld. Osborne depicts Jack as extremely cautious, wanting to think things through before acting, while Annie prefers to charge ahead. Their traits complement each other; sometimes he needs a push from his bold sister, and sometimes she needs him to rein in her recklessness. For example, Jack stops Annie from rushing across the bridge to the Otherworld: “‘Come on, let’s go!’ said Annie. ‘Wait!’ said Jack. ‘What about the guards?’” (45). His caution gives them time to concoct the plan with the invisibility cloak. Despite his timidity, Jack is a loyal friend who faces his fears and worries for Morgan’s sake:

He loved Morgan. She was their great friend and teacher. If he and Annie did not go on their quest, Morgan’s story and the stories of Camelot and all the stories about the magic tree house would end forever.