When gunpowder is set off, an explosion always follows. Accordingly, this chapter is well named. It has a twofold purpose: to relate the bank robbery and to show Louisa's growing fondness for Harthouse and her continued awakening to the realization that something is missing from her life.
The chapter opens with Harthouse smoking his pipe and musing over the happenings of the preceding night. Pleased with himself at the turn of events, he did not dwell long on the consequences of what could happen as a result of his relationship with Louisa. Here the reader sees Dickens drawing an analogy between Harthouse and the devil. Harthouse departs early for a public occasion, at some distance from the Bounderby residence. When he returns to the Bounderby house at six, he is met by Bounderby, who informs him of the robbery at the bank. Whoever entered the bank did so with a false key; the key was later found in the street. One hundred and fifty pounds is the missing sum. At the Bounderby house are Bitzer, who is scolded for sleeping so soundly, and Mrs. Sparsit, who has come to stay because her nerves are too bad for her to remain in her apartment at the bank. Bounderby comments that even Louisa fainted when she learned of the robbery. The reader realizes almost immediately the identity of the thief, but Stephen Blackpool is suspected of the crime. Coming under suspicion as an accomplice is the old woman who is yet a mystery to all. When Harthouse inquires concerning Tom's whereabouts, Bounderby says he is helping the police.
As the evening progresses, Mrs. Sparsit obliges her employer by occasionally resorting to copious tears as she caters to Bounderby's whims — playing backgammon with him and preparing his sherry with lemon-peel and nutmeg — and watches Louisa and Harthouse, hoping for the worst.
Louisa lies sleepless waiting for Tom's return; she is concerned, for she suspects that he — not Blackpool — has forced open the safe and used the false key, if indeed it were used. An hour past midnight she hears Tom enter. After giving him time to prepare for bed, she goes to his upstairs room, hoping that he will confide in her. They discuss their visit with Blackpool and Rachael and agree not to tell anyone about it. Tom lies to Louisa, telling her that he had taken Stephen outside on the stairs that night to tell him what good fortune he had in getting her help. Troubled, Louisa leaves her brother, who weeps, unable to confide in her or anyone else.