However eerie and unpleasant Scrooge's midnight adventures have been, they are all fun and games until the Ghost of Christmas Yet to Come shows up. This thing isn't even called a ghost any more—Dickens changes the terminology and starts referring to this super menacing cloaked figure as a "phantom."
The text doesn't really explain this word change, but we're guessing it has something to do with the fact that the other two Christmas ghosts were a lot more human in their behavior than this mutely pointing dude. (Also, Dickens might just have a thing about silent figures pointing fingers at the guilty. Check out the death of lawyer Tulkinghorn in Bleak House. It happens right under a painting of a guy pointing down at the corpse.)
The phantom's exit is a little more predictable than that of the other two ghosts. Sure, it's stressful when the thing disappears without telling Scrooge whether he'll get a do-over, but, hey, at least it's not birthing claw-footed babies in front him. It's the little things. Here is how the good-bye goes down:
"Are these the shadows of the things that Will be, or are they shadows of things that May be, only? […] Why show me this, if I am past all hope! […] Assure me that I yet may change these shadows you have shown me, by an altered life!" […]
In his agony, [Scrooge] caught the spectral hand. It sought to free itself, but he was strong in his entreaty, and detained it. The Spirit, stronger yet, repulsed him.
Holding up his hands in a last prayer to have his fate reversed, he saw an alteration in the Phantom's hood and dress. It shrunk, collapsed, and dwindled down into a bedpost. (4.151-166)
Scrooge has gone from fighting the ghosts off to trying desperately to hold onto them and not go back to his own reality. That's a pretty startling change, no? Again, is this a sign that he really has undergone some fundamental shift in his ability to empathize with others?
It was a little more marked during his good-bye with the Ghost of Christmas Present, when instead of losing it at the sight of the ghost-babies, Scrooge is instead worried about whether the ghost is okay.
But here, there is a clear difference as well—Scrooge is making an appeal to the phantom's sense of mercy and asking it to just have some pity on him and tell him the deal. Rather than attacking it, like he did with the Ghost of Christmas Past, Scrooge tries to find the emotional humanity in a startlingly inhuman figure.
This seems like a pretty big departure, and a mirror of what has happened to Scrooge himself. He has rediscovered his own humanity under all that cold.