Lucy is a talented young ghost hunter working at Lockwood & Co. after fleeing a traumatic previous employment in northern England. She possesses a rare psychic ability to hear the voices of spirits and sense the residual emotions tied to their deaths. Raised in a cold household, she relies on her fierce independence and strong survival instincts in a city overrun by paranormal threats.

Anthony Lockwood is the charismatic teenage owner and founder of Lockwood & Co. He operates the independent ghost-hunting agency out of his inherited home at 35 Portland Row. He has the psychic ability to see death-glows, the residual visual energy left behind by violent ends. He maintains a perpetually optimistic and polite exterior, even when facing severe supernatural danger or crippling financial trouble.

George is the resident researcher at Lockwood & Co. He rarely joins the front-line ghost hunts initially, preferring to stay back and study the history and origins of the spirits they face. He is meticulous, highly focused on preparation, and frequently frustrated by the impulsive decisions made by his coworkers.

Mr. Fairfax is the wealthy Chairman of Fairfax Iron, a company that produces the iron defenses necessary to protect against ghosts. He is a tall, thin man whose expensive clothing hangs loosely on his aged frame. He holds an undeniably commanding presence and knows exactly how to leverage his vast wealth to secure the services of desperate agencies.

Inspector Barnes is a strict officer from the Department of Psychic Research and Control (DEPRAC). His job involves overseeing the various ghost-hunting agencies in London. He holds a harsh view of independent, youth-run operations and makes no secret of his disdain for the amateurish mistakes made by young agents.

Hugo Blake is a man with a troubled past who is brought to the attention of DEPRAC. He maintains an eccentric, dapper style despite having an aged, sunken, and gaunt physical appearance. He carries a haunting energy that makes those around him deeply uncomfortable.

Annabel Ward is the spirit of a young woman who haunts the walls of a London home. In life, she was a passionate actor who died suddenly, leaving behind a gold necklace with a cryptic Latin inscription. As a ghost, her spirit is tethered to her physical remains and remains lost, cold, and highly dangerous to the living.

Mrs. Hope is an older woman experiencing a terrifying haunting in her recently acquired home. She hires Lockwood & Co. under the belief that the ghost of her recently deceased husband is wandering the staircase, unaware of the true entity lurking in the walls.

Susan Martin is Mrs. Hope's middle-aged daughter. She acts as a mediator for her mother, meeting the young ghost hunters at the property to let them inside. She is visibly skeptical of Lucy and Lockwood's youth, questioning their capabilities before leaving them to their work.

Jason is an adult supervisor at the first ghost-hunting agency where Lucy worked. He gradually loses his nerve for the job, becoming increasingly anxious and preferring to wait outside haunted locations while sending his team of child agents into danger.

Kipps is an older teenage boy who works as a team leader for the prestigious Fittes agency. He wears a coordinated uniform and enjoys using his agency's high status to demean independent operators. He maintains a bitter rivalry with Anthony Lockwood, often resorting to taunts and drawn weapons in public.

The Caretaker is a surly man employed to maintain the grounds of Combe Carey Hall. He holds a deep knowledge of the property's bloody history and guides visitors through the estate. He recounts gruesome historical events about the monks and madmen who previously inhabited the land.

Lucy's mother is an exhausted, emotionally distant woman who raised several daughters after her husband's death. Living in a world plagued by supernatural threats, she treats Lucy's psychic talents primarily as a source of income, taking her to work at a ghost-hunting agency at the age of eight.

Lucy's father was a cold and distant man who passed away when Lucy was five years old. Following the mandatory precautions of their ghost-plagued society, his body was laden with iron and silver to prevent his spirit from returning to haunt the living.

Mr. Hope is the recently deceased husband of Mrs. Hope. He passed away on the staircase of his home, leading his grieving widow to assume that his lingering spirit is the entity causing the terrifying supernatural disturbances in the house.