Annie is Jack’s seven-year-old little sister and the story’s other main character. Even though she’s the younger sibling, Annie is daring and actively charts the course of their adventure rather than tagging along behind her big brother. Osborne establishes Annie as an equal team member and a fellow protagonist with Jack by making her the first to scale the tree house’s ladder and the one who proposes ancient Egypt as their destination. Two of her most prominent traits are her bravery and her strong conscience. She demonstrates both when she fearlessly calls out to the mysterious figure because she wants to return the scepter to its rightful owner: “Come back, mummy! […] We want to help you!” (21). These strengths propel the plot forward because she’s not “scared at all” of Hutepi and promises to aid the ghost-queen while Jack remains paralyzed with fear (26). 

Annie has a playful personality and sometimes teases her nervous brother, but she cares deeply about Jack and encourages him when he’s afraid, supporting the novel’s thematic interest in Confronting the Unknown With Courage. Another characteristic that differentiates the siblings is Annie’s imagination. The young girl believes in magic, and this belief is vindicated by her encounters with the ghost-queen and the supernatural cat. The siblings’ contrasting views of the world provide humor, as in the scene when they debate the true nature of the procession. Jack’s argument that it’s only a mirage evidences his trepidation and fear. Annie forms a matter-of-fact rebuttal: “‘How could sunlight look like people, a mummy box, and a bunch of cows?’ […] ‘Ghosts,’ Annie said.” This introduces the existence of the supernatural within the world of the novel (15). Annie prefers hands-on educational opportunities that celebrate learning through discovery, making the chance to explore a pyramid highly appealing to her learning style. 

Osborne illustrates the importance of Solving Problems Through Cooperation through the way that Annie works with Jack to find the Book of the Dead, and by giving the siblings complementary traits that support their teamwork. By modeling how to face the unknown with courage, Annie helps Jack find his own bravery. For example, when Jack hesitates outside Queen Hutepi’s burial chamber, Annie keeps both Jack and the plot moving forward by reminding him, “She’s waited thousands of years for her book. Don’t make her wait anymore” (42). Annie’s daring is often a helpful counterbalance to her brother’s caution, but sometimes her impulsivity lands her and Jack in trouble. The scene in which the siblings become trapped in the false passage after Annie runs off by herself functions as a reminder of the importance of cooperation.

Queen Hutepi is the spirit of an ancient Egyptian royal laid to rest in the pyramid that Jack and Annie visit. Osborne conveys her regal nature through her poise, the opulent funerary treasures outside her burial chamber, and the narrator’s description of her majestic appearance in Chapter 4: “It was a lady. A beautiful Egyptian lady. The lady wore flowers in her black hair. Her long white dress had many tiny pleats. Her gold jewelry glittered” (24). One of the ghost-queen’s key traits is her patience. She waits thousands of years to enter the afterlife instead of risking passage through the Underworld without the Book of the Dead. She patiently teaches Jack and Annie about her culture and remains composed throughout the trial-and-error process of decoding the secret message. Osborne portrays the ghost as sympathetic rather than frightening, and Jack admires Queen Hutepi’s “kind and gentle” personality (37). The Magic Tree House books are known for being mild adventure stories suitable for very young readers, and Hutepi’s characterization helps to preserve this dynamic. Queen Hutepi’s kindness and plight appeal to the audience’s sense of empathy and increase Jack and Annie’s desire to help her.

Queen Hutepi is an essential supporting character, introducing the quest that serves as the plot’s main engine. Her request for help allows Jack and Annie to take on heroic roles and supports the novel’s key themes. Queen Hutepi contributes to the theme of learning through discovery by teaching the siblings about ancient Egyptian culture and the Book of the Dead. Seeing her mummy provides both Jack and Annie with an important learning experience. The children must collaborate with one another and with the ghost-queen to find her scroll, reinforcing the role of cooperation in solving problems. The stakes of the children’s quest center on Queen Hutepi's ability to escape the pyramid where she’s been trapped for millennia, find the Book of the Dead to secure her best hope of surviving perils like “[l]akes of fire. Monsters. Demons,” and finally gain access to the Next Life (27). The ghost-queen’s very existence forces Jack to confront his fear of the unknown and the limits of his knowledge because he doesn’t believe in specters before he meets her. Befriending the kindly ghost teaches the protagonist that the unexpected can be something positive rather than something frightening, and his determination to assist her helps him persevere through his fears and grow in courage.