Superstition and folk tales
The story opens with the folk tale of the Baskerville curse, presented on eighteenth century parchment. The reproduction of the curse, both in the novel and in Mortimer's reading, serves to start the story off with a bang-a shadowy folk tale, nothing if not mysterious. At the same time, it offers a nice contrast to Watson's straight-forward reporting, a style insisted upon by the master and one which will ultimately dispel any foolish belief in curses and hounds of hell.
A classic of the mystery/detective genre, the red herring throws us off the right trail. Much like the folk tale, it offers a too-easy answer to the question at hand, tempting us to take the bait and making fools of us if we do. In Hound, the largest red herring is the convict. After all, who better to pin a murder on than a convicted murderer. Barrymore's late-night mischief turns out to be innocent, and the convicted murderer turns out to not be involved in the mysterious deaths.