This chapter constitutes a word-for-word transcription of the letter Lanyon intends Utterson to open after Lanyon’s and Jekyll’s deaths. Lanyon writes that after Jekyll’s last dinner party, he received a strange letter from Jekyll. The letter asked Lanyon to go to Jekyll’s home and, with the help of Poole, break into the upper room—or “cabinet”—of Jekyll’s laboratory. The letter instructed Lanyon then to remove a specific drawer and all its contents from the laboratory, return with this drawer to his own home, and wait for a man who would come to claim it precisely at midnight. The letter seemed to Lanyon to have been written in a mood of desperation. It offered no explanation for the orders it gave but promised Lanyon that if he did as it bade, he would soon understand everything.
Lanyon duly went to Jekyll’s home, where Poole and a locksmith met him. The locksmith broke into the lab, and Lanyon returned home with the drawer. Within the drawer, Lanyon found several vials, one containing what seemed to be salt and another holding a peculiar red liquid. The drawer also contained a notebook recording what seemed to be years of experiments, with little notations such as “double” or “total failure!!!” scattered amid a long list of dates. However, the notebooks offered no hints as to what the experiments involved. Lanyon waited for his visitor, increasingly certain that Jekyll must be insane. As promised, at the stroke of midnight, a small, evil-looking man appeared, dressed in clothes much too large for him. It was, of course, Mr. Hyde, but Lanyon, never having seen the man before, did not recognize him. Hyde seemed nervous and excited. He avoided polite conversation, interested only in the contents of the drawer. Lanyon directed him to it, and Hyde then asked for a graduated glass. In it, he mixed the ingredients from the drawer to form a purple liquid, which then became green. Hyde paused and asked Lanyon whether he should leave and take the glass with him, or whether he should stay and drink it in front of Lanyon, allowing the doctor to witness something that he claimed would “stagger the unbelief of Satan.” Lanyon, irritated, declared that he had already become so involved in the matter that he wanted to see the end of it.
Taking up the glass, Hyde told Lanyon that his skepticism of “transcendental medicine” would now be disproved. Before Lanyon’s eyes, the deformed man drank the glass in one gulp and then seemed to swell, his body expanding, his face melting and shifting, until, shockingly, Hyde was gone and Dr. Jekyll stood in his place. Lanyon here ends his letter, stating that what Jekyll told him afterward is too shocking to repeat and that the horror of the event has so wrecked his constitution that he will soon die.