After all, the great American author was fascinated by ghosts and wrote about them on more than one occasion. For instance, in The Adventure of Huckleberry Finn, he even wrote that, "I heard that kind of a sound that a ghost makes when it wants to tell about something that's on its mind and can't make itself understood, and so can't rest easy in its grave, and has to go about that way every night grieving." If that's not the account of an author who knew about ghostly sounds, what is?
So, if you're fortunate enough to attend the lecture tonight - and even if you're not (although tickets are still available) - get into the spirit of the Twain house by reading this March 1866 article from a San Francisco weekly called The Golden Era, where the author relates an encounter with mediums and ghosts: