What happens when Scrooge sits down in front of the fireplace to warm himself?

After sitting down before the fireplace to eat his gruel, an long disused bell began to swing and ring of its own accord.

It was with great astonishment, and with a strange, inexplicable dread, that as he looked, he saw this bell begin to swing. It swung so softly in the outset that it scarcely made a sound; but soon it rang out loudly, and so did every bell in the house.