As the lawyers, the law clerks, and judges have retired for the day and as the evening wears on, Mr. Snagsby takes his post-dinner walk when he bumps into Mr. Weevil, who does copy work for Mr. Snagsby and who currently occupies the room where Mr. Snagsby's former employee Captain Hawdon lived and died. They are both uneasy, Mr. Snagsby on account of the business with Mr. Tulkinghorn and Inspector Bucket, which he is obligated to keep a secret and Mr. Weevil on account of business he is to have with Mr. Krook and Mr. Guppy tonight at midnight. When they part, unbeknownst to Mr. Snagsby, who is eager to return home at once so as to prevent worrying his wife, Mrs. Snagsby appears out of hiding to follow her husband home.
Presently, Mr. Guppy greets Mr. Weevil and lets him know that the secrecy of their business required him--Mr. Guppy--to avoid Mr. Snagsby. The subterfuge perturbs Mr. Weevil who isn't all too happy working for Mr. Guppy which requires him to spy on Mr. Krook with regard Mr. Krook's former tenant who has died, while living under Mr. Krook's roof and in the very room where the deceased former tenant had died. Consequently, Mr. Guppy chides Mr. Weevil, arguing that if anyone has a right to grieve then that person is none other than Mr. Guppy, a reference to his unrequited love vis-a-vis Esther Summerson.
As they wait for midnight in Mr. Weevil's room, Mr. Guppy notices a strange stain on his coat sleeve. The stain and an eerie smell compel Mr. Guppy to vigorously wash his hands when his right hand makes contact with the stain while leaning out of the window for fresh air. By and by, 12 PM strikes and Mr. Weevil goes downstairs to fetch Mr. Krook. Their business with Mr. Krook appertains to papers of Captain Hawdon's that Mr. Krook had illegally taken possession of. Mr. Guppy and Mr. Weevil have agreed to translate the meaning of those papers on behalf of Mr. Krook who is illiterate, or so Mr. Krook was made to understand. Indeed, Mr. Guppy intends to confiscate those papers in the name of the law though his reasons are for personal profit. Presently, Mr. Weevil returns prematurely, alone, and in a state of distress.
Mr. Guppy joins Mr. Weevil as he returns to Mr. Krook's room which is vacant save for Krook's cat which is snarling at a pool of an eerie and foul smelling thingabob on the floor. Then they realize the unthinkable. The pool of the eerie and foul smelling thingabob on the floor is Mr. Krook who has spontaneously combusted.