Gabriel John Utterson
Gabriel John Utterson, a lawyer and close loyal friend of Jekyll and Lanyon for many years, is the main protagonist of the story. Utterson is a measured and at all times emotionless, bachelor – who nonetheless seems believable, trustworthy, tolerant of the faults of others, and indeed genuinely likable. However, Utterson is not immune to guilt, as, while he is quick to investigate and judge the faults of others even for the benefit of his friends, Stevenson states that "he was humbled to the dust by the many ill things he had done". Whatever these "ill things" may be, he does not partake in gossip or other views of the upper class out of respect for his fellow man. Often the last remaining friend of the down-fallen, he finds an interest in others' downfalls, which creates a spark of interest not only in Jekyll but also regarding Hyde. He comes to the conclusion that human downfall results from indulging oneself in topics of interest. As a result of this line of reasoning, he lives life as a recluse and "dampens his taste for the finer items of life". Utterson concludes that Jekyll lives life as he wishes by enjoying his occupation.
Dr Henry Jekyll/Mr Edward Hyde
Dr Jekyll is a "large, well-made, smooth-faced man of fifty with something of a slyish cast", who occasionally feels he is battling between the good and evil within himself, leading to the struggle between his dual personalities of Henry Jekyll and Edward Hyde. He has spent a great part of his life trying to repress evil urges that were not fitting for a man of his stature. He creates a serum, or potion, in an attempt to separate this hidden evil from his personality. In doing so, Jekyll transformed into the smaller, younger, cruel, remorseless, evil Hyde. Jekyll has many friends and an amiable personality, but as Hyde, he becomes mysterious and violent. As time goes by, Hyde grows in power. After taking the potion repeatedly, he no longer relies upon it to unleash his inner demon, i.e., his alter ego. Eventually, Hyde grows so strong that Jekyll becomes reliant on the potion to remain conscious throughout the book.
Richard Enfield is Utterson's cousin and is a well known "man about town." He first sees Hyde at about three in the morning in an episode that is well documented as Hyde is running over a little girl. He is the person who mentions to Utterson the actual personality of Jekyll's friend, Hyde. Enfield witnessed Hyde running over a little girl in the street recklessly, and the group of witnesses, with the girl's parents and other residents, force Hyde into writing a cheque for the girl's family. Enfield discovers that Jekyll signed the cheque, which is genuine. He says that Hyde is disgusting looking but finds himself stumped when asked to describe the man.
Dr Hastie Lanyon
A longtime friend of Jekyll, Hastie Lanyon disagrees with Jekyll's "scientific" concepts, which Lanyon describes as "...too fanciful". He is the first person to discover Hyde's true identity (Hyde transforms himself back into Jekyll in Lanyon's presence). Lanyon helps Utterson solve the case when he describes the letter given to him by Jekyll and his thoughts and reactions to the transformation. After he witnesses the transformation process (and subsequently hears Jekyll's private confession, made to him alone), Lanyon becomes shocked into critical illness and, later, death.
Poole is Jekyll's butler who has been employed by him for many years. Poole serves Jekyll faithfully and attempts to be loyal to his master, but the growing reclusiveness of and changes in his master cause him growing concern. Finally fearing that his master has been murdered and that his murderer, Mr Hyde, is residing in Jekyll's chambers, Poole is driven into going to Utterson and joining forces with him to uncover the truth.
Utterson joins this Scotland Yard inspector after the murder of Sir Danvers Carew. They explore Hyde's loft in Soho and discover evidence of his depraved life.
Sir Danvers Carew, MP
A kind, 70-year-old Member of Parliament. The maid claims that Hyde, in a murderous rage, killed Carew in the streets of London on the night of 18 October. At the time of his death, Carew is carrying on his person a letter addressed to Utterson, and the broken half of one of Jekyll's walking sticks is found on his body.
A maid, whose employer - presumably Jekyll- Hyde had once visited, is the only person who has witnessed the murder of Sir Danvers Carew. She saw Hyde murder Carew with Jekyll's cane and his feet. Having fainted after seeing what happened, she then wakes up and rushes to the police, thus initiating the murder case of Sir Danvers Carew.