Bobby is a 15-year-old student living in Chicago. He reads extensively, plays the trumpet in his school jazz band, and frequently feels ignored by both his scholarly parents and his peers at the university's elite private school. His sudden lack of physical form forces him to move through his environment differently and pushes him to find the scientific cause of his condition.

Alicia is a smart 15-year-old girl who lost her sight two years prior to the events of the story. She takes correspondence classes to continue her education and feels socially isolated since her former friends drifted away. She is fiercely independent, quick-witted, and highly perceptive, refusing to accept pity from others.

Emily is a literature professor at the University of Chicago. She is authoritative, accustomed to commanding a classroom, and initially struggles to handle her son's bizarre predicament. Beneath her strict exterior, she is fiercely protective of her family and willing to fight authorities to keep them together.

David is a physicist at FermiLab who views the world through an analytical lens. He is often distracted by his work, leading to friction with Bobby, but his scientific expertise becomes vital when investigating the mechanics of the anomaly.

Leo is an astronomy professor at the University of Chicago with wild hair and an intense academic focus. He is highly protective of his daughter but quickly becomes fascinated by the scientific challenge Bobby presents.

Julia is Alicia's mother, a woman with a degree in English literature who previously worked in corporate public relations. She has set aside much of her life to care for Alicia and is highly protective of her daughter's social interactions.

Ms. Pagett is a truancy officer for the county board of health and the school district. She is persistent, observant, and determined to uncover the truth about Bobby's sudden disappearance, utilizing threats of legal action when obstructed.

Mrs. Trent is the nosy neighbor living across the street from the Phillips family. She actively looks for gossip and tries to pry into the household's business when Bobby is left alone.

Dr. Fleming is a physician at the hospital treating David and Emily following their collision. She is professional and concerned about Bobby's welfare while his parents are incapacitated.

Walt is a security guard stationed at the main library of the University of Chicago. He is familiar with the faculty children and regular students who frequent the building.

Aunt Ethel is Emily's relative who resides in Miami, Florida. She loves playing bridge and serves as a convenient cover story to throw truancy officers off Bobby's trail.

Sheila is a woman living in Miami who experienced a similar anomalous event years prior. She earns a living designing websites and has adapted to her unique circumstances in a warm climate.

Amber works in the legal department at the Sears corporate offices. She strictly adheres to company privacy policies and refuses to release customer information over the phone.