These ghosts, sometimes referred to as "spirits" in both the novel and the play adaptation will take Scrooge on a hellish night of time-travel that will be the catalyst for a major paradigm shift in how he approaches his life. The first, the Ghost of Christmas Past, takes Scrooge back to exactly that--his past. Scrooge sees himself alone and lonely as a little boy at boarding school, left there by his cruel father at Christmastime; he sees his sister come to get him, a few Christmases later, after their father has agreed to let him return home; he sees a Christmas party he attends as a young apprentice, given by his first employer, Fezziwig, and he is witness to the Christmas his fiancee breaks their engagement because Scrooge's priorities have become about money, and she has no dowry. This ghost reminds him how painful it was to be rejected, how much he loved his little sister, Fan, how much his first employer's generosity meant to him as a young apprentice, and how his priorities cost him what might have been a long and happy marriage.
The Ghost of Christmas Present, resplendent in a wild fur-lined, green robe, takes Scrooge to see how various people are celebrating Christmas, beginning with his employee, Bob Cratchit, whose impoverished family is making the best of what little they have, thanks to Bob's meager earnings at the hands of the tight-fisted Scrooge. The Cratchits appreciate being together, and try not to dwell on their poverty, or the illness that threatens their youngest child's life. This ghost also shows Scrooge a group of poor miners in camp, and a crew on a ship at sea celebrating the holiday, and then the Christmas party at his nephew's house, where everyone is very merry. Scrooge becomes aware at this point of two things: 1) Christmas celebrations apparently aren't as linked to money as he thought they were, and 2) he himself is not terribly popular with his employee, his nephew, or their respective friends and family. This ghost also reminds Scrooge of the societal problems of Ignorance, and Want, and uses Scrooge's own words against him: "Are there no prisons? Are there no workhouses?"
The final ghost, the Ghost of Christmas Future, shows Scrooge how his own death will be received if things do not change: businessmen joking in the street about how cheap his funeral is likely to be, and discussing how they really don't want to go unless lunch is involved, others mentioning his death in the same sentence as the weather forecast, and thieves pawning his possessions at a pawn shop even as they joke about what a miser he was and how it didn't bother them to steal from him.
When Scrooge awakens on Christmas morning and realizes that it's not too late, he is a changed man. The man who the day before told his nephew that "every idiot who goes about with 'Merry Christmas' on his lips, should be boiled with his own pudding, and buried with a stake of holly through his heart," begins to "keep Christmas well" by raising Cratchit's salary, giving him time off, making amends with his nephew, paying for Tim Cratchit's lifesaving medical care and even becoming a sort of surrogate father to Tim.