Zach is a fourteen-year-old boy living in a luxurious Fifth Avenue apartment in Manhattan. Following the sudden death of his father, he discovers he is developing superpowers, including enhanced speed, strength, and heightened senses. An indifferent student but a natural athlete, he struggles with his grief, his temper, and the daunting new responsibilities of his emerging abilities.

Kate is the intelligent and grounded teenage daughter of the Harriman family's housekeeper. She has grown up alongside Zach and serves as his closest confidante. While lacking superpowers, her sharp intuition, bravery, and steady loyalty make her essential to Zach as he faces his dangerous new reality.

A mysterious, white-haired older man who appears in Zach's life shortly after Tom Harriman's death. He possesses knowledge of the "magic" running through the Harriman bloodline and takes it upon himself to train Zach. Cryptic and demanding, he forces Zach into dangerous situations to accelerate his learning.

Zach's father and a troubleshooting diplomat for the US president. He is a superpowered "hero" who battles global evil, keeping his dangerous double life a secret from his wife and son. His sudden death in a plane crash leaves a massive void in his family and passes his extraordinary abilities down to his son.

The long-time Harriman family attorney and Tom's closest friend. Known affectionately as "Uncle John" to Zach, he steps in as a surrogate father figure following the tragedy. He warns Zach against trusting Mr. Herbert and claims to know the truth about the dangerous world Tom operated in.

Zach's mother, born Elizabeth Townsend. She directs the charitable Townsend Foundation and copes with the loss of her husband by throwing herself into political campaigning. Unaware of her husband's—and now her son's—superpowers, she tries to maintain safety and structure for her grieving family.

A mysterious, shadowy syndicate of evil individuals bent on global destruction and power. Tom Harriman spent his life fighting them, and their existence looms over Zach as he learns to use his new abilities. They represent the ultimate, unseen threat facing the "hero."

A US Senator and leading presidential candidate who attended Harvard with Tom Harriman. He is a charismatic politician whose campaign focuses on integrity and service. He serves as an idealized figure of leadership that Zach and his mother look up to following Tom's death.

The student body president and basketball team captain at Parker School. He is arrogant, easily jealous, and frequently bullies Zach, specifically targeting the boy because of Zach's close friendship with Kate.

An anonymous young man wearing a knit cap who repeatedly shows up in Central Park to harass and physically challenge Zach and Kate. He serves as an early, persistent physical test for Zach's emerging combat abilities.

The cook and housekeeper for the Harriman family who previously served as Zach's nanny. She is a stern but loving presence in the household, effectively serving as an informal member of the family and providing strict guidance to her daughter, Kate.