Richard Enfield and his cousin, Gabriel John Utterson, are strolling according to their usual Sunday custom when they come upon an empty building on a familiar street. Enfield remarks that some time previously he had seen an ill-tempered man knock down and trample a small child at the doorway of the deserted building. He and other indignant bystanders had forced the stranger, who gave his name as Hyde, to pay a sum of money for the child’s welfare. Enfield remembers Hyde with deep loathing.
Utterson has reasons to be interested in Hyde. He is a lawyer, and he drew up the strange will of Dr. Henry Jekyll. This will stipulates that in the event of Jekyll’s death, all of his wealth will go to a man named Edward Hyde. Utterson now seeks out Hyde, the man whom Enfield had described, to discover if he is the same person who had been named heir to Jekyll’s fortune.
Utterson finds Hyde, who is suspicious of Utterson’s interest and shuts his door in his face. Utterson next questions Jekyll, who refuses to discuss the matter and insists that in the event of his death the will must be executed as written. Utterson fears that Hyde is an extortionist who is after Jekyll’s money and will eventually murder the doctor.
About one year later, Hyde is wanted for the senseless murder of a kindly old gentleman named Sir Danvers Carew. Jekyll presents the lawyer and the police with a letter signed by Hyde, in which the murderer declares his intention of fleeing England forever. The letter ends with Hyde’s apology to Jekyll for having abused his friendship.
About this time, Dr. Hastie Lanyon, who had been for years a great friend of Jekyll, becomes ill and dies. A letter addressed to Utterson is found among his papers. When Utterson opens this missive, he discovers that it contains an inner envelope that is sealed and bears the directive that it is not to be opened until after Jekyll’s death. Utterson suspects that this mysterious sealed letter is also somehow connected with the evil Hyde.
One Sunday, Enfield and Utterson are again walking in the street where Enfield had seen Hyde abusing the child. They now realize that the deserted building holds a side entrance to a laboratory that is connected to Jekyll’s home. As they look up at the house, they see Jekyll sitting at a window, looking disconsolate. Then his expression seems to change, and his face takes on a grimace of horror or pain. Suddenly, he closes the window. Utterson and Enfield walk on, too overcome by what they had witnessed to be able to speak.
Not long afterward, Jekyll’s manservant, Poole, contacts Utterson to speak of his concerns that, for the past week, something strange had been going on in Jekyll’s laboratory. The doctor had hidden himself in his laboratory, ordering his meals to be sent in and writing curious notes demanding that Poole go to apothecaries in London in search of a mysterious drug. Poole is convinced that his master has been slain and that the murderer, not Jekyll, is hiding in the laboratory.
Utterson and Poole return to Jekyll’s house and break into his laboratory with an ax. As they enter, they discover that the man in the laboratory had just killed himself by draining a vial of poison. The man is Hyde. Utterson and Poole search in vain for the doctor’s body, convinced that it must be somewhere, since there is a note from Jekyll to Utterson dated this very day. In the note, Jekyll says he is planning to disappear, and he urges Utterson to read the note that Lanyon had left at the time of his death. An enclosure contains Jekyll’s confession.
Utterson returns to his office to read the letters. The letter of Lanyon describes an occasion when Jekyll had sent Poole to Lanyon with a request that the doctor search for a particular drug in Jekyll’s laboratory and give it to Hyde. Then, in Lanyon’s presence, Hyde had taken the drug and then transformed into Jekyll. The shock of this transformation had caused Lanyon’s decline in health, which led to his death.
Jekyll’s own account of the horrible affair is more detailed. He had begun early in life to live a double life. Publicly, he had been genteel and circumspect; privately, however, he had practiced strange vices without restraint. Becoming obsessed with the idea that people have two personalities, he had reasoned that people are capable of having two physical beings as well. Finally, he had compounded a mixture that transformed his body into the physical representation of his evil self. He became Hyde. In this disguise he was free to haunt the lonely, narrow corners of London and to perform the darkest acts without fear of recognition.
Jekyll did everything he could to protect himself in his disguise. He cautioned his servants to let Hyde in at any hour, he took an apartment for Hyde, and he made out his will in Hyde’s favor. His life proceeded safely enough until he awoke one morning in the shape of Hyde and realized that his evil self had appeared even without the drug. Frightened, he determined to cast off the persona of Hyde. He sought out better companions and tried to occupy his mind with other things. He was not strong enough, however, to continue to resist the immoral pleasures that the Hyde persona allowed him to enact. When Jekyll had finally permitted the repressed Hyde persona to emerge, Hyde was full of rage and an overpowering lust to do evil; thus, he murdered Carew.
After the murder, Jekyll had renewed his effort to abandon the nature of Hyde, but one day, walking in the park, he suddenly changed into Hyde and was forced to ask Lanyon to obtain the drug that would change him back to Jekyll. From that day on, the nature of Hyde asserted itself repeatedly. When his supply of chemicals had been exhausted and could not be replenished, Jekyll, as Hyde, shut himself up in his laboratory and experimented with one drug after another. Finally, in despair, Jekyll killed himself.