The book centers on Frannie Devin O'Neill, a veterinarian, whose husband was killed three years before the story takes place. The action takes place in Bear Bluff, Colorado. She meets Kit Harrison, an FBI agent, when he rents a cabin in the woods behind her house. One night, after a friend's mysterious death, Frannie sees a small girl with wings, running in the forest. Her name is Max, and they learn about Max's missing brother, Matthew, and the sinister place where they grew up. Kit, Frannie, and Max find and break into the School. They find the rest of Max's "flock", two Chinese/Asian siblings named Wendy and Peter, a blind boy named Icarus, and Oz, all of whom have wings. The group leaves the school and Kit calls the FBI for help. They try to go back to Frannie's vet clinic, the Inn Patient, but they find it burnt down. They are caught by the "whitecoats" (who work at the School) and the flock's previous Keeper, a cruel man named Harding Thomas (also known as "Uncle Tom"). .
Note: This book's characters are distinct from those in the Maximum Ride series, even though some have the same names.
An eleven-year-old girl with long blonde hair and emerald-green eyes. She is Matthew's older sister. She has white wings with silver-blue markings. Her wingspan is a little over nine feet. Frannie states that Max's IQ is in the 180s, although Max herself says that it is only 149. Her name is short for "Maximum," and her test-subject name is "Tinkerbell".
Dr. Frannie O'Neill
The veterinarian who finds Max.
An FBI agent who is supposed to be on vacation in Nantucket after a horrible tragedy killed his wife and his kids. He lives in the cabin in the woods behind the veterinary hospital. He has blond hair.
Named after Ozymandias, a fictional character in the poem by the same name, he is second-born and alpha male. He would be the leader of the flock if Max died, and Max is glad that Ozymandias is there. He is not much younger than Max, and he appears to be, in some ways, stronger than she. He has brown hair, green eyes, and, of course, wings.
A blind kid whom Max rescues from the "School." The flock communicates with him using chirps and whistles so that he doesn't get lost, flying. He has fine, long, ash-blond hair. He is named after Icarus from the Greek legend.
Named after Peter Pan, he is Wendy's twin. They are four years old, and therefore classified as "the young ones" by Oz and Max. They are of Chinese descent, with black bowl-cut hair. They are in the high-genius IQ range.
Named after Wendy from Peter Pan, she is Peter's twin. She has white wings, tipped with blue. According to Max, she calls all older women, "Mama".
Max's brother. He loves his sister and tries to keep her away from the Doctors after she escapes. He is codenamed 'Peter Pan'. His wings are white, with silver and dark-blue markings.
Works with the scientists. He is possibly codenamed 'Uncle Thomas'. He pretends to be kind to Matthew and Max to try to find out information or lure them back to the school, but is cruel if they refuse to cooperate.
Adam's sister. The flock believed they were 'put to sleep' when they were babies, but they survived. According to Max, their IQ is 'off the planet'.
Eve's brother. He was adopted by Gillian, Frannie's best friend, who renamed him Michael. He has blond hair. His life expectancy is 200 years, however he dies in a car crash at age four. When the flock is being held captive in Gillian's house, he helps Kit and Frannie escape to find them. He was born in the same year as Peter and Wendy, 1994, and was their closest friend. Like his sister, he was believed to have been 'put to sleep'.
Frannie's best friend as well as Michael (and Eve's) mother, although it is uncertain as to whether they are biologically related or adopted. Although she seems smart and sympathetic, she is actually closely related to the School and was keeping an eye on Frannie after her husband's death. Gillian later holds Frannie, Kit, and the flock hostage at her house and tries to sell the bird children to rich companies. When that plan fails, she, her husband, and Michael try to escape but are killed in a car wreck.
The head of the School. He created the School and impregnates women to have children for the School. He works at an invitro clinic where he delivers babies. The mothers are told by him that the babies are dead, when in reality they have been brought to the school.