Richard Mayhew
Richard is the main character and protagonist of the novel, and his life suddenly changes when he finds an injured girl named Door. Richard is told by his fianceé to not help Door, but he proceeds to do so anyway.
Richard then becomes a citizen of London Below, which consists of people who cannot be seen by regular citizens of "London Above". Richard's heroism is displayed as he assists Door in escaping an assassin in London below, but his flaws are revealed as he slowly loses his mind watching London Above move on without him.
Door
A young woman who is a member of a powerful and influential family in London Below. She has the ability to open any door, which makes her a valuable ally to have on a journey through the hidden landscape of the city. Door is strong-willed and resourceful, and she is determined to avenge the deaths of her family at the hands of Mr. Croup and Mr. Vandemar, two ruthless assassins who have been hired to kill her.
Mr. Croup and Mr. Vandemar
Mr. Croup and Mr. Vandemar are two complimentary characters who are the hired assassins of Door. Mr. Croup is talkative while Mr. Vandemar rarely talks; Mr. Croup always knows what is going on and Mr. Vandemar is the follower. The pair rarely separate during the novel and practically serve as two halves of the same person.
The marquis de Carabas
A sly and cunning trickster who helps Richard and Door on their journey through London Below. The marquis is charming and manipulative, and he is skilled at using his wit and charisma to get what he wants. He is also deeply loyal to his friends, and he is willing to risk his own safety to protect them.
Hunter
A fierce and skilled warrior who joins Richard and Door on their journey. Hunter is a skilled fighter and has a strong sense of loyalty to her friends. She is also fiercely independent and is determined to forge her own path in life.
The rat-speakers
A group of intelligent and resourceful rats aids Richard and his companions on their journey through London Below. The rat speakers are able to communicate with humans and are highly respected in London Below for their intelligence and resourcefulness.
The Angel Islington
A powerful and mysterious being who dwells in London Below and plays a significant role in the story. The Angel Islington is ancient and wise, and he is said to have the ability to grant wishes. However, he is also a mysterious and enigmatic figure, and his motives are not always clear.
Old Bailey
A member of Door's family who helps to guide Richard and Door on their journey. Old Bailey is wise and experienced, and he is a valuable ally to have on a journey through London Below.
Jessica
Richard's fiancée, who is unaware of his involvement in the world of London Below. Jessica is kind and compassionate, but she is also practical and level-headed. She is initially concerned about Richard's sudden disappearance, but she eventually comes to understand the importance of his journey.
Mr. Stockton
Richard's boss, who is initially dismissive of his concerns about Door. Mr. Stockton is focused on his own career and is unwilling to take risks or stray from a conventional path. However, he eventually comes to respect Richard's determination and bravery.
