Scrooge hates Christmas, happiness, generosity, and puppies probably.
He yells at his clerk for getting Christmas Day off with pay, tells off his nephew for inviting him to dinner, and chases away a guy soliciting charity.
That night, he goes home and hallucinates that his doorknocker is the head of his dead partner. After dinner, Marley's ghost shows up to tell him to change and warns of three more ghosts.
First is the Ghost of Christmas Past, who is a weird old man child.
The ghost takes Scrooge way back in the day, to see himself as a small sad little boy all alone at boarding school at Christmas, as an older boy whose sister fetches him from school with the cryptic info that their dad is all better now, as an apprentice at a Christmas party at Fezziwig's house, and as a young man whose fiancée breaks the engagement off because she knows that Scrooge is already married… to money.
Real-time Scrooge is super depressed by these memories and starts to think that he needs to be better to the people in his life.
Second, we have the Ghost of Christmas Present—basically a half-drunk frat guy.
Christmas Present is at first kind of anonymous, compared to Christmas Past.
Scrooge sees a lot of scenes of people really doing it up Christmas-style all over the country.
Then, the ghost goes in for the emotional kill—we see the house of the poor Cratchit family, who make up in love what they lack in money. After some more random people's Christmases, Scrooge sees a really fun party at his nephew's house.
The last visitor is the terrifying phantom of the Ghost of Christmas Yet to Come.
Scrooge sees a bunch of business dudes talking very lightly about someone who died and whom they clearly don't give a darn about, some servants pawn a bunch of stuff stolen from a dead guy whom no one was protecting, and a dead body with no mourners.
Oh, and he sees the Cratchits who are overwhelmed by the death of Tiny Tim and the fact that the other kids have to work some horrible jobs.
Finally, in a graveyard, the phantom shows Scrooge his own grave. Scrooge freaks out and begs for another chance to fix his life.
He wakes up in his own bed, on Christmas Day. Quickly, he orders a giant turkey for the Cratchits, donates money to charity, and goes off to Fred's house for the party.
And he becomes a totally upstanding member of the community forever afterwards.