Born to Margaret Shelburne as a result of rape by the Tall Man, Harold was raised in a carnival as an attraction and his mother's protector. Because Margaret never stopped spoiling him as he grew, Harold not only weighed 136 kilograms by his later years, but somehow retained his child-like mindset his entire life to the point that he never grew out of diapers. Because of this, Harold and Margaret were taunted and teased upon at every turn.
One day, some circus workers kidnapped Margaret as a cruel joke on Harold. In a rage-fueled search for his mother, Harold ransacked most of the carnival, and when he found her, she had suffocated in the bag the workers had kept her in. Enraged, Harold killed the circus workers responsible for Margaret's manslaughter with an axe and put their remains on display for paying customers.
When the carnival broker, Jimbo, found out what Harold had done, he ordered an angry mob to confront and horribly execute Harold.
Following their deaths, Harold and Margaret's spirits remained bound to earth, and were captured by Cyrus Kriticos to become The Great Child and Dire Mother. The two were then moved to the basement of Basileus's Machine with the other ten ghosts.
Dennis encounters The Great Child and The Dire Mother in their containment cube in the basement. The two ghosts were presumably either the seventh and eighth, or eighth and ninth ghosts to be released.
They appear before Dennis and Maggie in the hallways of the house, scaring them off. Later, a Latin chant causes The Great Child and The Dire Mother, along with the other ten ghosts, to go to the center of the machine and power it up.
When The Great Child, The Dire Mother and the other ghosts are freed from the trance, they throw Cyrus into a rotating crest of rings, killing him. The house then explodes, destroying its walls, and freeing The Great Child, The Dire Mother and the other ten ghosts.
- Axe: In death, he still carries the axe he used to kill the other circus freaks when he was looking for his mother. He's never seen using it, but it's implied that he knows how to use it in death.
- Originally, Harold died when he choked on his own vomit. However, the producers changed this as they felt it was too weak a backstory for him.
- It is unknown why The Great Child, as a ghost, appears as he did in life, while most of the other ghosts normally appear as they looked like after or at the moment they died. However, according to Cyrus, when Harold was killed, his body was mutilated "beyond what you or I could comprehend"; this is probably the reason the Child appears as he did before he died.
- Naturally, the sounds associated with the Great Child are infantile whimpers.
- Strangely, the Latin inscription beneath the symbol for The Great Child and the Dire Mother in The Arcanum, "Mures", is the Latin word for "mice"...
- He is the fourth male ghost in the zodiac.
- His ghost file is represented by a baby rattle.
- He is the only known ghost to have been the child product of rape.
- He is also a bastard child, as his parents were never married.