Mary is a fair-haired Yorkshire woman with clear blue eyes and a face made memorable less by beauty than by watchfulness. Her gaze goes first to thresholds, windows, and the empty space just above a visitor's shoulder, as if checking whether something followed them in. She smells faintly of lanolin, woodsmoke, and damp wool, a scent she knows clings to her clothes and does not apologize for. Her hair is usually twisted into a practical knot, but loose strands catch on the tiny burrs of her shawl. She moves with a weaver's economy: shoulders tucked, hands busy, feet finding the quiet boards. An unexpected detail for a fearful young mother is that she can whistle sharply enough to stop a room of quarrelling adults, a habit learned from calling sheep across a windy hillside.

Mary is warmly attentive in ordinary company, remembering how people take their tea and mending a torn sleeve without being asked. When she feels watched or deceived, that warmth becomes precise scrutiny: she asks plain questions and studies what a person avoids answering. She is tender with William but can be stern with adults who dismiss her concerns. In private with Oswin she can still laugh at his adventure stories; on nights when his shadow changes, she keeps the scissors in her hand and the iron thimble beside her son's bed.

Mary grew up in Yorkshire among wool, weather, and practical warnings about things that should not be invited over a threshold. She married Oswin Hirst for the quick mind behind his traveler's stories and the tenderness he showed when he thought no one was watching. On their wedding night, she expected her husband. Instead, in the candle's dying light, she saw a headless shape where Oswin should have been, with two red, saucer-like eyes burning in the blank air. Oswin later claimed she had dreamed. Mary remembers the weight of the arms around her and the wrongness of the shadow on the wall. She loves the man she remembers, and fears the creature that sometimes wears his place. Their son William was born with black hair despite both parents being blond, and vivid blue eyes that resemble Oswin's. He is slower to speak and learn than other children his age, though Mary refuses to let neighbors call him cursed. A later baby died sickly soon after birth, and Mary has since struggled to carry another pregnancy to term. She keeps iron scissors on her person and an iron thimble near William. She has told her father what she saw; her brother knows enough to be uneasy, but neither has confronted Oswin. Mary watches husband and son especially when the seasons turn and the boundaries grow thin. She has noticed Oswin never seems to age and avoids iron with a care too practiced to be coincidence. When the boundary thins, Oswin often guards the house, though his shadow sometimes changes shape before he does.