Twelve-year-old Alex is the thoughtful and observant narrator of the story. He founds the original Sherlock Society mystery club due to his interest in logic, puzzles, and the legacy of Sherlock Holmes. His hobbies include building complex LEGO models without instructions, pointing to a natural patience and a methodical approach to problem-solving. As the investigator in charge of geography, he handles the 'where' aspect of the group's cases.

Zoe is Alex's thirteen-year-old sister and the driven leader of the Sherlock Society Detective Agency. Initially frustrated about missing out on a trendy summer camp with her popular friends, she pitches the agency as a way to gain financial independence. She is intelligent, highly competitive, and handles the 'when' aspect of their investigations by managing timelines.

Grandpa is a seventy-three-year-old retired journalist for the Miami Herald who acts as the Sherlock Society's 'Director of Transportation and Logistics.' He drives a mint-condition 1964 aquamarine Cadillac convertible named Roberta. He mentors the children by teaching them the journalistic principle of the 'Five Ws' and grants them access to his storage unit filled with old case files.

Lina is a quiet but bold new student with electric-blue hair who recently moved to Miami from Evanston, Wyoming. She is an avid reader with extensive knowledge of mystery novels, which proves highly useful to the detective agency. Operating as the 'who' specialist of the group, she focuses on analyzing people, details, and relationships during their investigations.

Yadi is Alex's best friend since second grade and the technology expert of the Sherlock Society. An aspiring filmmaker who once appeared in a pizza commercial, he brings technical expertise to the team through his drone piloting and video editing skills. He is loyal, enthusiastic, and handles the 'what' aspect of the team's investigative framework.

Morris Kane is the wealthy CEO of Kane Crystals, a multigenerational family sugar company in Belle Glade. While he carefully cultivates a public image as a charming environmentalist, his ownership of the destroyed yacht *Sweet Caroline* places him at the center of a Secret Service inquiry. Special Agent Tyree's interest in him suggests that his sunny public relations facade conceals darker corporate secrets.

Aaron Pettigrew is Morris Kane's nephew and serves as the director of security for Kane Crystals. A heavily tattooed former police officer, he functions as a tough enforcer for his uncle's business operations. His presence around Kane's properties raises the suspicions of the young detectives as they dig deeper into the company's affairs.

Melinda is Alex and Zoe's mother and a formidable trial attorney known as the 'Lawyer of Lost Causes.' She initially attempts to shut down the children's detective agency due to legal and safety concerns, but she eventually provides crucial legal guidance. She establishes strict boundaries while aggressively negotiating with federal agents to protect her family.

Alex and Zoe's father is a laid-back marine biology professor at the University of Miami who focuses on coral reef preservation. Though he frequently travels for fieldwork, including a trip to Honduras, he provides critical scientific knowledge and laboratory access to assist the children with water testing. He offers essential emotional wisdom regarding social conformity.

Dale Tyree is a Special Agent with the Secret Service who travels from Washington to investigate corporate activities in Miami. He questions the Lassiter family after they are rescued from the destroyed yacht, offering them immunity deals in exchange for their cooperation and intelligence.

Joe Moody is a retired editor who formerly worked at one of the small newspapers owned by Kane Crystals. He provides the Sherlock Society with background information about his former employer's suspicious financial practices and aggressive corporate management.

Mr. Bailey is the owner of Bailey's Bait & Tackle Shop, located along Alligator Alley in the Everglades. He shares local legends about the skunk ape with the children and maintains surveillance cameras around his isolated business.

Virginia Jackson is the granddaughter of Al Capone's former plantsman. She preserves her grandfather's meticulous plant diaries and provides the young detectives with key historical clues in exchange for a promised donation to a literacy program.

Brooke is one of Zoe's popular middle-school friends. She and Chelsea form an exclusive social circle that heavily influences Zoe's initial desire to earn money for summer camp.

Chelsea is a close friend of Zoe and Brooke. Her focus on exclusivity and status represents the superficial social dynamics Zoe attempts to maintain at the start of the summer.

Officer Gonzalez works for the Miccosukee Police Department. He receives the drone footage from the young detectives but notes that his department lacks the resources to pursue off-reservation investigations.

Ms. Campos is the school librarian who designs an elaborate escape room game to test the deductive skills of the original Sherlock Society members.