At 12 years old, Alex narrates the story as a thoughtful and observant founder of the original Sherlock Society, focused on mysteries and logical puzzles. His development throughout the story includes embracing risk for important causes.

Pete Lassiter, Zoe and Alex's grandfather, acts as the mentor with a journalistic background, providing insights into investigation techniques and city history. He brings both wisdom and a mischievous spirit to the group.

A recent arrival from Wyoming, Lina is a key member of the Sherlock Society known for her quiet observation skills and extensive knowledge of mystery novels. Her attention to detail and outsider perspective contribute significantly to the group.

Best friends with Alex since second grade, Yadi is the tech-savvy member who loves conspiracy theories. His imaginative thinking aids the group's unconventional problem-solving tactics.

A corporate executive, Kane projects an image of a civic-minded environmentalist but serves as a primary antagonist for his ulterior motives that drive the central conflict.

As Morris Kane's nephew and director of security, Pettigrew acts as the enforcer, participating in the darker dealings that threaten the protagonists' investigation.

Melinda, a dedicated trial attorney, often challenges her children's detective work due to safety concerns but eventually supports their efforts as she embodies the family's moral principles.

The easygoing marine biologist father lends his scientific knowledge and wisdom to his children, reinforcing the story's themes surrounding the importance of family values.