There are actually two criminals in Arthur Conan Doyle's The Hound of Baskervilles. The first one to be captured is Seldon, or Notting Hill Murderer. He turns out to be the brother of Mrs. Barrymore, who is married to Barrymore, the butler of the Baskerville estate. Mrs. Barrymore has been planning to help her brother emigrate to South America and start a new life. The existence and location of Seldon are revealed by Barrymore's signal light. Seldon manages to evade capture. Unfortunately, Barrymore's generosity in giving Seldon an old suit of Sir Henry's clothing leads to the hound, who tracks by scent, chasing Seldon and Seldon falling off a cliff and dying. Watson and Holmes hear Seldon's screams and discover his body.
Holmes recognizes Stapleton from London. An interview with Laura Lyons confirms that Stapleton is up to no good. Holmes sets a trap by pretending to have left for London. Sir Henry acts as bait, and when the hound attacks Sir Henry, Holmes shoots the hound. As the detective and Holmes close in, Stapleton escapes onto the moor at night in the fog. It is presumed that Stapleton died in one of the bogs somewhere in the moor, but his body is not actually discovered.