William is a small, watchful child whose chin dimples sharply when he concentrates. His front teeth are broad and slightly crowded, and he chews the inside of his cheek while trying to decide whether an adult is telling the truth. His hair is painstakingly combed into a side part each morning, though by noon it has sprung into soft, unruly waves. He walks with the careful, heel-first steps of someone used to sleeping near creaking floorboards, then suddenly darts with startling speed when he recognizes a safe face. He has an unexpectedly immaculate collection of tiny pressed leaves tucked into his coat pocket, each arranged by shape.

William wants to be brave and useful, but he is still a child who needs reassurance. With Mary he is affectionate and talkative; with unfamiliar adults he becomes observant and guarded. When relaxed, he is easily delighted by small discoveries. When frightened, he becomes stubbornly quiet and tries to solve the problem alone.

William is Mary Hirst's young son, raised above the small rooms where she mends nets and hems work clothes for the people of Brackenford. He remembers little of his father, who vanished before William could speak, but he remembers the winter Mary carried him through floodwater wrapped in her own coat when the river broke its banks. That night changed her: since then, she checks every latch twice and will abandon a job without explanation if she thinks danger is near. William has learned the habits of a child who wants to be useful without adding to his mother's burdens. He knows the safest lanes between the quay and home, can identify neighbors by their footsteps, and quietly leaves food scraps for a one-eyed alley cat. Mary has never told him that she privately doubts whether the man she once loved was truly his father. Now a stranger has asked after William by name, and Mary is weighing whether staying in Brackenford is more dangerous than leaving the life they know.