A very pale boy with a narrow, watchful face and black hair that grows in thick, uneven waves, refusing the neat part his nurse tries to give it. His skin has the almost translucent cast of someone raised indoors through long winters, but his cheeks redden quickly in the moor wind. He moves without the restless fidgeting adults expect: when waiting, he places his weight on the balls of his feet and tips his head as if measuring a sound beyond the room. His hands are often smudged with peat or chalk. The unexpected detail is that he keeps small, carefully folded paper birds in his pockets and gives them names.

William is observant but slow to put observations into words, and he can seem distant until something catches his interest. He wants his parents' approval yet resists being handled as a fragile possession. In calm company he is gentle and unexpectedly funny; under scrutiny he becomes stubbornly silent. Outdoors, where adults stop testing him, he grows curious and decisive.

William was born after a long, exhausting labor that left Mary Hirst feverish and Oswin Hirst silent with fear. When Oswin first held his son, he did so with a solemn care that the household remembered more clearly than any words. The infant's black hair and Oswin's bright, burning blue eyes became family talk before William could speak. As he grew, he learned words and lessons more slowly than other children, and the household's concern sharpened into arguments over whether he could one day inherit. His maternal uncles Edmund and Huge, along with his maternal grandparents, worry that the boy will be judged incapable; Mary tries to shield him from their scrutiny, while Oswin watches him for signs of what he calls 'moor-creature ways.' That phrase has hurt William even when he did not understand it. A formative change came during a winter outing when William wandered from the house and was found beside a spring, dry and uninjured, with a flock of ravens gathered around him. Since then, he has been drawn to the moor's sounds and patterns. Now the family faces pressure to name a suitable heir, while William has begun waking before dawn and insisting that something beneath the hill is calling through the ground.