What is disclosed in chapter 15 of The Hound of the Baskervilles?

"Chapter 15: A Retrospection" is the final chapter of The Hound of the Baskervilles by Sir Arthur Conan Doyle. In this chapter, Holmes and Watson are back in London, approximately a month after the major action of the story and the presumed death of Stapleton and rescue of his wife, Beryl. Sir Henry and Dr. Mortimer are passing through London on their way to taking a sea voyage. In this chapter, the four men meet, and Holmes explains in some detail his detection procedures and additional information about the case.
The most important thing that is disclosed is family history. The most crucial thing Holmes reveals is that Stapleton was a pseudonym and that the man calling himself Stapleton was actually the son of Sir Charles's younger brother. This explain Stapleton's motivation for the murders. He was attempting to kill off his older relatives in order to inherit the Baskerville estate, to which he felt entitled. He ties up a few other loose ends, including the theft of the boot being something Stapleton did to give the dog Sir Henry's scent. Beryl is shown in some detail to be an abused wife who deserved to be rescued.