Utterson and his kinsman Enfield walk past a mysterious door and Enfield tells the story of watching Hyde trample a young girl without remorse, then buy silence with a cheque signed by Jekyll.

Utterson reads Jekyll's will, consults with Dr Lanyon about Jekyll's 'unscientific balderdash,' and stakes out the laboratory door to intercept Hyde — their meeting leaves him deeply unsettled.

Utterson confronts Jekyll at a dinner party and demands to know the truth about Hyde. Jekyll insists it is all in hand, asks Utterson to protect Hyde if Jekyll is 'taken away,' and seems surprisingly comfortable.

A maid witnesses Hyde beat Sir Danvers Carew, an MP, to death in the street with a cane. The police contact Utterson. They search Hyde's ransacked Soho flat and find half a burnt cheque-book — Hyde has vanished.

Utterson visits Jekyll's laboratory, finds him looking ill and shaken, and sees a letter supposedly from Hyde. Utterson's clerk Guest observes that the handwriting is similar to Jekyll's — and Utterson concludes Jekyll forged the letter to protect Hyde.

Jekyll emerges briefly into society, then seals himself away again. Lanyon's health collapses overnight after some undisclosed 'shock.' Lanyon dies and leaves Utterson a sealed letter: open only after Jekyll's death or disappearance.

Utterson and Enfield see Jekyll at his laboratory window. He looks desperately sad. He begins to join them for a walk, then something crosses his face — and he slams the window shut. Both men walk away in silence, unable to speak.

Poole comes to Utterson in a panic — Jekyll has been locked in his laboratory for weeks, the voice inside doesn't sound like him, and Poole believes his master was murdered. Utterson and Poole break down the door and find Hyde dead in Jekyll's clothes. Jekyll is gone. Two letters remain.

Lanyon's sealed letter: Jekyll sent him urgent instructions to retrieve chemicals from the laboratory and deliver them to a stranger. The stranger mixed the compound before Lanyon and transformed back into Jekyll. The shock destroyed Lanyon.

Jekyll's confession: his double nature, the discovery of the compound, the initial euphoria and freedom of Hyde, the loss of control, the involuntary transformations, the murder of Carew, the attempt to stop, the failure. The final lines: the last transformation is coming. This is his last writing as himself.