The Unbreakable Code

James is Emily’s best friend and a fellow seventh grader who lives in the apartment upstairs. His parents run a Chinese catering business and rent out the apartment to Emily’s family. Their friendship is close and collaborative; they send encoded notes to each other using a bucket pulley system between their windows. James shares Emily’s passion for books and puzzles and is just as engaged in Book Scavenger as she is. Cheerful, energetic, and intelligent, James brings humor and lightness to their shared investigations. His trademark unruly cowlick, which he calls Steve, mirrors his playful and self-aware personality.

Though often upbeat, James is not without his own emotional challenges. His father travels frequently for work, and James quietly resents the distance this creates in their relationship. He hopes that finding the treasure will convince his father to stay home more. James’s storyline parallels Emily’s in the way both kids hope to use the discovery of treasure to secure the stability they crave in their families. His partnership with Emily is central to the novel; their collaboration showcases the theme of mutual support and the idea that curiosity and problem-solving are best pursued with a friend.

Mr. Quisling, Emily’s social studies teacher, begins the novel as a somewhat rigid but fair presence in the classroom. However, he gradually becomes a more complex and sympathetic character. A longtime fan of Book Scavenger, Mr. Quisling originally joined the game to connect with his son after a divorce. His investment in the unbreakable code is deeply personal and tied to a longing for reconnection and redemption. Over the course of the book, readers learn that he once helped excavate the Niantic, a buried ship linked to San Francisco’s Gold Rush history and to the coded message Emily is trying to solve.

Mr. Quisling is ultimately revealed to be a red herring in the mystery. He behaves secretively, giving readers (and Emily and James) the impression that he may be behind the fires. His uncommon surname—which he shares with Norwegian Prime Minister Vidkun Quisling (1887-1945), a Nazi collaborator—has become a word used to describe someone who collaborates with an immoral authority. This surname is another instance of misdirection, suggesting that Quisling may be acting in the service of some more powerful villain who has not been identified. Instead, he is the target of Mr. Sloan’s plan for revenge. Quisling’s confusion about who Coolbrith really is, and his belief at different points that it could be his son or his old friend Miranda, reveals his vulnerability and emotional isolation. His growing bond with Ms. Linden by the novel’s end hints at the possibility of healing and reconnection.

Mr. Sloan, who goes by the alias “The Phoenix,” is the novel’s antagonist. A former teacher who lost his job after an explosive classroom accident, Sloan blames Mr. Quisling for his dismissal. He adopts the Coolbrith persona to lure Mr. Quisling into a false sense of connection, only to orchestrate a string of arson attacks and frame him. The Phoenix’s fixation on fire stems from unresolved childhood trauma; he was bullied and called “fire freak” as a kid. His actions reflect a desire for control, recognition, and revenge. Sloan’s storyline illustrates how resentment can fester when left unaddressed and how tools like codes, stories, and books that bring people together can also be misused when driven by pain.

Matthew is Emily’s older brother and serves as both a foil and a source of support. With his bold clothing choices, love of music, and effortless charisma, Matthew represents the kind of confidence Emily wishes she had. Yet he is also a supportive sibling who joins Emily and James on their adventure when it matters. His ability to make others laugh and open up contrasts with Emily’s internal hesitations, and his presence offers levity to the story’s more serious moments.

Hollister is the owner of the bookstore where Emily spends much of her time. A kind and book-loving adult with long dreadlocks and a friendly demeanor, Hollister is a mentor figure to Emily, giving her a place to feel grounded and valued. His history with Mr. Griswold and his decision to let Emily help around the store speak to his belief in community and young people’s potential. Even after a devastating fire, Hollister never blames Emily and remains determined to rebuild. His resilience and generosity echo the novel’s broader theme of hope.

Mr. Griswold is the flamboyant and eccentric founder of Book Scavenger. After being attacked in a previous book, he has become more reclusive and anxious. He wears more subdued clothing, stays in his office or home, and keeps his dogs near him at all times. Emily notices this change and takes it upon herself to try to rekindle his passion and help him return to the community he built. Her efforts succeed, and Mr. Griswold re-emerges to support both the school dance and Hollister’s bookstore, planning a new Book Scavenger event on Alcatraz. His arc explores themes of recovery and the healing power of being seen and supported by your community.

Charlie is a college student hired to help with Hollister’s website. Though early clues point to him as the culprit behind the string of fires, Charlie serves as a red herring in the mystery. He lies about his coding skills, disappears during the fire, and holds a past grudge against Mr. Quisling. While he is ultimately not the villain, he is still held accountable for his dishonesty and irresponsibility and fired for leaving Emily alone in the store during the fire.

Emily’s parents are adventurous and spontaneous, which creates some tension with their daughter’s growing desire for stability. They dream of living in every state and frequently move their family to new places in pursuit of an exciting life. Since they are both freelancers, they struggle with the financial strain of living in an expensive city like San Francisco. Despite their desire to travel, they are supportive and thoughtful of Emily and hear out her desire to stay. When Emily’s dad is offered a job at Bayside Press, he checks to make sure Emily is comfortable with it before taking it. In the end, their choice to stay in San Francisco validates Emily’s emotional journey and deepens her sense of home.