I learned to recognise the thorough and primitive duality of man . . . if I could rightly be said to be either, it was only because I was radically both.
This chapter offers a transcription of the letter Jekyll leaves for Utterson in the laboratory. Jekyll writes that upon his birth he possessed a large inheritance, a healthy body, and a hardworking, decent nature. His idealism allowed him to maintain a respectable seriousness in public while hiding his more frivolous and indecent side. By the time he was fully grown, he found himself leading a dual life, in which his better side constantly felt guilt for the transgressions of his darker side. When his scientific interests led to mystical studies as to the divided nature of man, he hoped to find some solution to his own split nature. Jekyll insists that “man is not truly one, but truly two,” and he records how he dreamed of separating the good and evil natures.
Jekyll reports that, after much research, he eventually found a chemical solution that might serve his purposes. Buying a large quantity of salt as his last ingredient, he took the potion with the knowledge that he was risking his life, but he remained driven by the hopes of making a great discovery. At first, he experienced incredible pain and nausea. But as these symptoms subsided, he felt vigorous and filled with recklessness and sensuality. He had become the shrunken, deformed Mr. Hyde. He hypothesizes that Hyde’s small stature owed to the fact that this persona represented his evil side alone, which up to that point had been repressed.
Upon first looking into a mirror after the transformation, Jekyll-turned-Hyde was not repulsed by his new form; instead, he experienced “a leap of welcome.” He came to delight in living as Hyde. Jekyll was becoming too old to act upon his more embarrassing impulses, but Hyde was a younger man, the personification of the evil side that emerged several years after Jekyll’s own birth. Transforming himself into Hyde became a welcome outlet for Jekyll’s passions. Jekyll furnished a home and set up a bank account for his alter ego, Hyde, who soon sunk into utter degradation. But each time he transformed back into Jekyll, he felt no guilt at Hyde’s dark exploits, though he did try to right whatever wrongs had been done.
It was not until two months before the Carew murder that Jekyll found cause for concern. While asleep one night, he involuntarily transformed into Hyde—without the help of the potion—and awoke in the body of his darker half. This incident convinced him that he must cease with his transformations or risk being trapped in Hyde’s form forever. But after two months as Jekyll, he caved in and took the potion again. Hyde, so long repressed, emerged wild and vengefully savage, and it was in this mood that he beat Carew to death, delighting in the crime. Hyde showed no remorse for the murder, but Jekyll knelt and prayed to God for forgiveness even before his transformation back was complete. The horrifying nature of the murder convinced Jekyll never to transform himself again, and it was during the subsequent months that Utterson and others remarked that Jekyll seemed to have had a weight lifted from his shoulders, and that everything seemed well with him.
Eventually, though, Jekyll grew weary of constant virtue and indulged some of his darker desires—in his own person, not that of Hyde. But this dip into darkness proved sufficient to cause another spontaneous transformation into Hyde, which took place one day when Jekyll was sitting in a park, far from home. As Hyde, he immediately felt brave and powerful, but he also knew that the police would seize him for his murder of Carew. He could not even return to his rooms to get his potions without a great risk of being captured. It was then that he sent word to Lanyon to break into his laboratory and get his potions for him. After that night, he had to take a double dose of the potion every six hours to avoid spontaneous transformation into Hyde. As soon as the drug began to wear off, the transformation process would begin. It was one of these spells that struck him as he spoke to Enfield and Utterson out the window, forcing him to withdraw.
In his last, desperate hours, Hyde grew stronger as Jekyll grew weaker. Moreover, the salt necessary for the potion began to run out. Jekyll ordered more, only to discover that the mineral did not have the same effect; he realized that the original salt must have contained an impurity that made the potion work. Jekyll then anticipated the fast approach of the moment when he must become Hyde permanently. He thus used the last of the potion to buy himself time during which to compose this final letter. Jekyll writes that he does not know whether, when faced with discovery, Hyde will kill himself or be arrested and hanged—but he knows that by the time Utterson reads this letter, Henry Jekyll will be no more.