Who suddenly appears to Scrooge on the door knocker, and what does he say to Scrooge?

When Scrooge puts his key into the lock, the knocker on his front door eerily turns into the face of his old business partner Jacob Marley, who has been dead for several years. The knocker does not actually speak to Scrooge (although Marley will have quite a bit to say to him later on, once Scrooge gets settled in upstairs). However, Marley’s eyes seem to be wide open, though they do not move, and his hair sort of blows softly around as though some warm breath or current of air were moving it. Perhaps this phenomenon is caused by the gusting heat coming from the fires of Hell. After all, we find out soon enough that Marley has certainly gone to a place of punishment after his death.