How It All Goes Down
Early in the play, we meet an old cheapo named Harpagon whose only concern in life is his cash. He's so obsessed with money, in fact, that he nearly tries to strip search everyone who goes in and out of his house. We also find out that ol' Harpagon has buried a small box filled with a lot of money (10,000 French crowns, which is a ton in the 17th century) in his backyard that he's paranoid about someone stealing. At this point Harpagon is sounding like a dog with a favorite juicy bone.
Meanwhile, it looks like Harpagon's son Cléante and daughter Élise have both fallen in love. But Harpagon wants Cléante's lover Mariane for himself and wants Élise to marry a rich old man named Anselme. Cléante and Élise hatch a plot to make Harpagon give up his designs so they can finally be happy. Harpagon isn't so easily fooled, though. He soon figures out Cléante's scheme and threatens to disown the boy for daring to speak against him. Nice parenting, H.
In the play's final act, Cléante's valet—named La Fléche—digs up Harpagon's backyard treasure and makes off with it. Harpagon goes totally ape and calls the police. He demands that the culprit be found and hanged, because he's totally level-headed like that. Cléante, however, assures Harpagon that he'll get his money back as soon as he agrees to let Cléante marry Mariane and to let Élise marry her lover Valère. Harpagon only agrees after finding out that the man he wants Élise to marry—Anselme—is actually the long-lost father of both Valère and Mariane. How convenient! What's more important, though, is that Anselme is prepared to pay Harpagon a tidy sum to make the old man just go away and stay out of everyone else's business.
At the end of the play, the lovers go off to get married and live happily ever after while Harpagon is left to grow old with his money. There's no Ebenezer Scrooge moment in this play. Harpagon hasn't changed at all, and he only has his moneybags to keep him warm at night. Womp, womp.