Dr. Henry Jekyll/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, thus 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 mask this hidden evil within his personality. However, in doing so, Jekyll transforms into the smaller, younger, cruel, remorseless, evil Hyde. Jekyll has many friends and has an amiable personality, but as Hyde, he becomes mysterious and violent. As time goes by, Hyde grows in power. After taking the potion repetitively, 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.
Stevenson never says exactly what Hyde takes pleasure in on his nightly forays, generally saying that it is something of an evil and lustful nature. Thus, in the context of the times, it is abhorrent to Victorian religious morality. Hyde may have been revelling in activities that were not appropriate to a man of Jekyll's stature, such as engaging with prostitutes or burglary. However, it is Hyde's violent activities that seem to give him the most thrills, driving him to attack and murder Sir Danvers Carew without apparent reason, making him a hunted outlaw throughout England.
Realizing he will soon be Hyde forever, Jekyll leaves behind a testament, pointing out that while Jekyll often felt like a charlatan, Hyde felt like a "genuine man" years younger and far more energetic than his more "sociable" self. He also states in his final confession that although Hyde knew people recoiled from him, he did not recoil from them.
Stevenson's pronunciation of Jekyll used a "long e" sound (/iː/), which was the pronunciation used in Stevenson's native Scotland. This is also the pronunciation of Gertrude Jekyll. This notwithstanding, the accepted pronunciation of Jekyll in Standard US and UK English employs a short e ( dʒɛk.l̩ ).
Gabriel John Utterson
Gabriel John Utterson, a lawyer and loyal friend of Jekyll's (and Lanyon's), is the character the narrator focuses on, and follows in Utterson's quest to discover the identity of Hyde. Utterson is a measured, and at all times emotionless, bachelor – who nonetheless seems believable, trustworthy, tolerant of the faults of others, and indeed genuinely likeable. Utterson has been close friends with Lanyon and Dr. Jekyll. 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-falling, 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.
Richard Enfield is Utterson's distant relative and is a well known "man about town", suggesting a certain sexual licentiousness. Evidence to support this is that he first sees Hyde at about three in the morning in an episode that is well documented as Hyde running over a little girl. He is the person who mentions to Utterson the actual personality of Jekyll's heir, 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's, Hastie Lanyon disagrees with his "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. When Lanyon witnesses the transformation process (and subsequently hears Jekyll's private confession, made to him alone), Lanyon becomes critically ill and later dies of shock. As an embodiment of Victorian rationalism, materialism, and scepticism, Lanyon serves as a foil to Jekyll.
Poole is Jekyll's butler who has lived with him for many years, upon noticing the reclusiveness and changes of his master, goes to Utterson with the fear that his master has been murdered and his murderer, Mr Hyde, is residing in the chambers. Poole serves Jekyll faithfully, and attempts to do a good job and be loyal to his master. Yet events finally drive him into joining forces with Utterson to find 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, white-haired old man and an important 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 (sometime between 11 pm and 2 am by the testimony of the maid). At the time of his death, Carew is 70 years old and is carrying on his person a letter addressed to Utterson. As a result, the police subsequently interview Utterson with regard to the murder. Although there is no clear reason for his murder, Carew openly greets Hyde immediately prior to the killing. Coupled with this, both characters have a direct link to Utterson.
A maid, whose employer Hyde had once visited, is the only person who claims to have witnessed the murder of Sir Danvers Carew. She states that she believes Hyde murdered Carew. She faints after she sees what happens, then wakes up and rushes to the police, thus initiating the murder case.