Ted is a 12-year-old boy living in South London who uses meteorology to understand the world around him. Operating on a "different operating system," he has an intensely logical mind but struggles to interpret social cues, body language, and figurative speech. His methodical thinking and obsession with details make him uniquely suited to investigating his cousin's disappearance, even when his stressed parents dismiss his observations.

Kat is Ted's teenage sister, characterized by her energetic, outgoing, and impatient personality. She frequently frustrates her highly logical brother but possesses a fierce independence and a willingness to break rules. When Salim disappears, she becomes desperate to uncover the truth and slowly learns to value Ted's unique mind over her own emotional reactions.

Gloria is Faith's sister and Salim's mother, a stylish art curator preparing to move from Manchester to New York. Known by Ben as "Hurricane Gloria" due to her intense emotional energy, she brings a chaotic atmosphere to the Spark household. She is deeply attached to her son and becomes physically ill and entirely distraught when he goes missing.

Salim is Ted and Kat's 13-year-old cousin, a tall, pensive teenager with a love for photography and tall buildings. He is quietly unenthusiastic about his mother's plans to relocate them to a fast-paced life in New York. His inexplicable disappearance from a sealed capsule on the London Eye sets the story's central mystery in motion.

Ben is Ted and Kat's father, a building-demolition expert currently preparing to tear down an abandoned public-housing high-rise called the Barracks. He uses humor to manage family tensions and initially provides stability for the household. However, as the crisis deepens, he struggles to balance his children's desire to investigate with his wife's intense emotional distress.

Faith is Ted and Kat's mother, a busy nurse who has a strained history with her sister, Gloria. She is highly protective of her family and tries to keep order in her small house. When her nephew goes missing, her stress levels skyrocket, causing her to become harshly dismissive of Ted's investigative theories and intensely strict with Kat.

Detective Inspector Pearce is the methodical, straightforward police officer assigned to locate Salim. Unlike the panicked family members, she maintains a calm, logical demeanor that brings comfort to Ted. She is one of the few adults willing to listen to Ted's analytical deductions without brushing him aside.

Rashid is Salim's father and Gloria's ex-husband. He lives separately from them and has a contentious relationship with Gloria. He frequently argues with her about their differing views on parenting, money, and Salim's future, but unites with her in front of the media to plead for his son's safe return.

Christy is a man working security at a motorcycle exhibition hall. He approaches the children in line at the London Eye and gives them his ticket, claiming a sudden fear of heights and claustrophobia. His strange actions and patterned t-shirt make him a person of interest when Kat and Ted attempt to trace their cousin's last known steps.

Marcus is a boy from Manchester who befriended Salim after they both faced severe bullying at school. The two boys bonded over their shared experiences and their roles in a school production of *The Tempest*, becoming close companions. He is deeply upset by Salim's impending move to New York.

Mr. Shepherd is one of Ted's teachers who provides him with practical, systematic ways to understand human behavior. By teaching Ted a five-point facial expression guide, he offers the boy a logical framework for interpreting people's moods, making him a trusted figure in Ted's life.