During a walk Richard Enfield tells his cousin Utterson a gruesome story: Some time ago a shady character named Hyde had ruthlessly knocked a little girl to the ground and then trampled over the child. By paying a larger sum the matter was cleared up at first. However, Utterson cannot forget this story, especially since he knows who paid the money: his client and friend Dr. Jekyll. Back home, Utterson examines Jekyll's will, which was recently unconditionally changed by Jekyll in favor of Hyde in the event of his death or "disappearance without a trace", and which was given to Utterson for safekeeping. On the same evening he visits an old friend of Jekyll, the doctor Dr. Hastie Lanyon. Utterson hopes to find out more about the connection between Jekyll and Hyde...