What story does Pearl hear of her mother’s involvement with "The Black Man" of the Forest in The Scarlet Letter?

Pearl first overhears the story of Hester and "The Black Man" from an old woman who thinks Pearl is asleep, but Pearl doesn't speak to Hester about it until Chapter 16, "A Forest Walk."  It is also important to note that Pearl is present in Chapter 8 when Mistress Hibbins asks Hester to join "The Black Man" in the forest among the coven of witches.  On their forest walk, however, Pearl demands that Hester tell a story and then asks her about this Black Man who "offers his book and an iron pen to everybody that meets him among the trees; and they are to write their names with their own blood" (177).  Further, Pearl reveals that "the old dame said that this scarlet letter was the Black Man's mark on thee, and that it glows like a red flame when thou meetest him ad midnight, here in the dark wood" (177).  Hester's response to all of Pearl's questions is quite simple and is the only true thing that Pear hears of her mother's involvement in all of this:  "Once in my life I met the Black Man! . . . This scarlet letter is his mark!" (178).