Although the streets of London and Soho where Mr. Hyde pursues his evil business recall the dark and seedy strains of the Gothic, the primary Gothic setting in the story must be Dr. Jekyll's laboratory building. A Gothic setting is often an old, decaying edifice, perhaps empty except for the supernatural creatures that haunt it, or a secret, forbidden wing or room in an occupied building. Jekyll's laboratory is a separate wing or building from his main home, and it is accessed through a courtyard. Stevenson foreshadows the final scene of the story when Utterson and Enfield, on their "usual walk," take the "back way to Dr. Jekyll's." There, standing in the "premature twilight" of the courtyard, they see Dr. Jekyll in an upper window. After a short, depressing conversation with him, they see his face change to an "expression of ... abject terror," and he slams the window down.
Later, when Poole comes to get Utterson, they make their way into the laboratory building. Its surgical theater is piled high with crates and bottles. There is a stairway leading to the locked "cabinet," a room from which agitated pacing, screams, and cries have been issuing for days. Poole has been leaving meals outside the door, and they are smuggled in when no one is looking. Orders for strange drugs appeared for Poole to fill. One day Poole found a disfigured dwarf digging among the crates; the "masked thing like a monkey" ran away from the chemicals up the stairs and locked himself in the cabinet.
Poole and Utterson proceed to break down the door with an ax; they find Edward Hyde's body twitching from the last throes of death. They then explore the rest of the laboratory building, looking for the body of Jekyll. There are empty closets filled with dust and cobwebs and a spacious cellar filled with ancient "crazy lumber." A "perfect mat of cobweb" falls when they open the sealed entrance. They go back to the cabinet and analyze its contents, trying to figure out the mystery.
Stevenson's presentation of the laboratory as a Gothic setting enhances the "strange case" that Utterson must solve.