Dr. Lanyon recounts that he received a letter from Jekyll the day after they dined together with Utterson and their other friends. The letter instructed Lanyon to go to Jekyll’s house, break into his laboratory, and pick up a drawer from his cabinet containing chemical powders and a phial. The letter said to bring this to his own home, then meet a messenger from Jekyll and consign it to him.

Lanyon does as he is instructed. At midnight, he meets a stranger at his house who is in reality Hyde. Hyde mixes a potion and, telling Lanyon that he is about to witness “a prodigy to stagger the unbelief of Satan” (108), drinks it. With violent convulsions, his form changes into that of Jekyll. Over the next hour, he tells Lanyon all about his double life, an account that “sickens” and shakes Lanyon to his roots (109). 

Jekyll recounts that he started out as an honorable, moral and industrious individual. However, along with this virtuous nature there was “impatient gaiety of disposition” and a tendency to “irregularities” that led to a “profound duplicity of life” (110). Jekyll wondered if it might be possible to separate out the good and the evil parts in man, thus ending the eternal moral struggle in man’s soul.