Jax is the 12-year-old protagonist and viewpoint character of the novel. He is an ordinary tween who lives in New York City, but unusual color-changing eyes mark his appearance. High stress triggers them to turn dark blue while hypnotic visions turn them purple. He learns that the color-changing eyes run in his father’s family, and he later discovers that his hypnotic abilities are tied to his eyes and family history. Midway through the novel, Jax learns that his mother comes from a line of notable hypnotists as well, the Sparks family, whose tree includes Frances Mesmer, the most famous hypnotist in history. Being the confluence between two notable hypnotist bloodlines causes Jax to have unusually strong powers.

Throughout the novel, Jax's relationships with others drive his character arc. His friendship with Tommy is a source of comfort and normalcy, but ultimately, Jax must prioritize Tommy's safety over their bond. His relationships with Mako and Braintree represent opposing forces: Mako embodies the dangers of unchecked power and manipulation, while Braintree offers guidance and support, recognizing that hypnotic powers come with great temptation and hypnotists must use them sparingly. Jax is close with his parents but sees how his hypnotic powers put them in danger and erode the trust between them.