Kent's form is unmistakably male and not a taller or altered version of Mary's: a handsome young man with a long, clean-lined face, short bright-blond hair that lies neatly even after a night outdoors, and vivid malachite-green eyes. His skin is pale, his jaw narrow but firm, and his teeth are unusually even; when he laughs, it is a quick, surprised flash, as if laughter escaped before good manners could catch it. He stands taller than Mary, with a lean, well-fed-looking frame that seems faintly out of place beside Rochester's tired workers. His hands are smooth enough to suggest he has never hauled a coal scuttle, but he keeps inspecting his cuffs as if willing them to fit. He moves with careful, indoor composure until startled, when he turns his whole body toward a sound like someone unused to being watched. Unexpected detail: he is fascinated by practical, grubby domestic repairs and will study a mended kettle or a child's patched shoe with the solemn interest of a museum visitor.

Mary is resourceful and protective, but her competence has been forced on her so early that she rarely admits when she is overwhelmed. She can be patient with the small children and sharp with adults who try to exploit them. Kent's manner is more shy, proper, and home-loving than Mary's, and he wants to be seen as respectable; still, curiosity can draw him toward a beach, a tree, or a derelict building. Mary sometimes reads his propriety as ordinary male behavior and resents it, while also relying on it to keep them from attracting attention.

Mary Bell is eighteen, the oldest of eight children in an isolated house near Rochester, Kent. Neglectful parents left her with much of the childcare and whatever schooling she could steal between chores. Her father Simon Bell was often away working, and his return brought old arguments back into the house. Her mother Malinda Bell drank heavily and had children by different men: Chrissy, whose father is unknown and Jamaican; and Belladonna, whose paternity is also uncertain. Simon brought home Jonas, a five-year-old blond boy with vivid blue eyes, from one of his absences. Mary tries to shield Matilda, twelve, from being turned into her replacement as unpaid caretaker. She also worries about Henry, fourteen, whose new cunning and rowdiness sometimes turn against her, and tries to make time for little Abigail, Oswald, and the other children even when there is no time to spare. On Mary's eighteenth birthday, Malinda brought home an odd stone she had found lodged in a log. Mary was grateful for the gesture, though she did not think the stone was jewelry and did not expect Malinda to remember giving it to her. Later it began beating in time with Mary's heart. In mirrors, her reflection gradually became a blond young man with green eyes. Mary thought it a cruel trick, then a frightening nuisance, then one more problem she could not afford to investigate. The first time she woke in Kent's body after a bad dream, she was horrified. By dawn, she had discovered that the change could give her a way out of the house. It did not feel to her like a second life or a great mystery; it felt like a chance to walk somewhere without being called back to another chore. Her first night out as Kent began when she woke in the wrong body, found a shirt and trousers that almost fit, and slipped outside before the household stirred. She walked toward the river, climbed a tree she would never have risked as Mary, and explored a derelict building with a sagging roof. The adventure stopped being carefree when she realized she had no reliable clothes to change into if the transformation reversed. She made it home near dawn, muddy and exhilarated, and spent the morning inventing an excuse for her absence. On another early trip, Simon returned sooner than expected. Mary, as Kent, heard his key and had to get back into the house without being seen. She hid behind the coal shed, then slipped through a side entrance when Simon went to fetch something from the yard. From the kitchen she heard him and Malinda begin their familiar argument. The narrow escape taught her that an outing could end with her trapped outside her own home, and that Kent's face could make a stranger of her to the people she loved. One evening, a very drunk Malinda encountered Kent in the house and mistook him for a visitor or a young man from Simon's work. She offered him a glass, asked intrusive questions, and let slip how exhausted she was with the family. Mary tried to keep Malinda from recognizing the shape of her own child beneath the unfamiliar face, answering with stiff, careful phrases. Malinda briefly treated Kent with more attention than she usually gave Mary, which left Mary with a sour mixture of relief and anger. She got Malinda safely to bed and hid before morning, carrying the knowledge that being seen as someone else could change how her mother behaved. Kent's first pub visit was meant to be a quick look at the town and a warm drink. The room was loud, smoky, and full of men who assumed he belonged there. He sat carefully, ordered something plain, and listened more than he spoke. A patron tried to draw him into boasting about work; Kent's replies were self-conscious and faintly prim, but not unkind. He disliked the spilled beer, the rough jokes, and the sticky table, yet stayed because the pub offered a kind of adult freedom Mary rarely had. He was fascinated by the regulars' confidence and quietly appalled by their manners. When he spotted Henry, the encounter became awkward: Henry looked at Kent as a stranger, while Mary knew exactly how quickly her brother could make trouble. She left before Henry could follow, taking the long way home. Mary's friend Trudy, a short, skinny young woman with dirty-blond hair and hazel eyes, calls herself a rebel and dresses in an alternative style for the early Cold War years. She notices how tired Mary is and helps with the children. In one memorable event, Trudy came by on a wet afternoon and found Kent trying to keep Abigail and Oswald occupied while the other children were out of the room. Rather than demand an explanation, Trudy handed him a towel, helped settle the little ones, and quietly covered for him when a neighbor passed the window. She later told Mary she knew something strange was happening but would wait to hear it in her own time. Kent found Trudy's directness alarming and her kindness difficult to dismiss. A separate daylight change happened early in the morning at home, while the youngest children were awake. Mary was trying to keep Oswald from crying, stop Abigail from reaching a hot kettle, and find breakfast while the older children were still asleep. The shift came in the middle of the kitchen's bustle. The children noticed that the person in front of them had changed; Oswald clung to his blanket and watched Kent cautiously, while Abigail treated him as a new playmate. Mary kept the kettle safe and the children calm until she changed back. The incident convinced her that the changes were not limited to nights or private escapes. Kent is more shy than Mary supposes, wants to be regarded as respectable, and carries the indoor habits and middle-class English sensibilities of a homebody. He prefers a tidy room, a proper introduction, and a planned visit, even while his existence repeatedly sends Mary climbing trees and sneaking into pubs. He does not have an entirely separate stream of thought: his preferences, reactions, and knowledge arise within Mary's experience, and she often mistakes them for ordinary male behavior. Henry later said he stole and sold the heart-stone. It is now missing, and Mary does not know whether he still has it or whether he understands its connection to Kent.