Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Exposition (Initial Situation)
All of London is abuzz after a wealthy heir named John Harmon dies on his way to England. But the plot thickens when everyone realizes that he didn't just die—someone murdered him! So now all of John Harmon's inheritance money goes to a pair of servants named Mr. and Mrs. Boffin.
This inheritance leaves a woman named Bella Wilfer in the cold, because one of the conditions of John Harmon's inheritance was for him to marry Bella Wilfer and share his life (and fortune) with her. The Boffins feel bad about Bella's poor luck, so they take her on as their adopted daughter anyway. In another part of London, a guy named Eugene Wrayburn develops a crush on a pretty, working-class girl named Lizzie Hexam. The only problem is that Lizzie has another male admirer who hates Eugene's guts.
Rising Action (Conflict, Complication)
Once the Boffins have all kinds of money, people start approaching them looking for ways to get in on their cash. A man named John Rokesmith applies to be Mr. Boffin's secretary and succeeds. But over time, Boffin becomes paranoid about his money and suspicious of everyone around him, even the good people.
He hires a man named Silas Wegg to read to him in the evenings, but Wegg is secretly planning to blackmail Boffin for the lion's share of his fortune. In the meantime, Eugene Wrayburn continues his courting of Lizzie. But his romantic rival Bradley Headstone is stalking him and planning to murder him. Way to handle rejection smoothly, Headstone.
Climax (Crisis, Turning Point)
Eventually, Mr. Boffin's greediness and paranoia become so strong that he fires his secretary, Mr. Rokesmith, for no reason. Bella Wilfer is so aghast at Boffin's actions that she decides to walk away from him and his money. She loves Mr. Rokesmith and wants to marry him.
Oh yeah, and it turns out that Mr. Rokesmith is actually John Harmon in disguise. So John Harmon isn't dead and now he gets to inherit all his father's fortune… if he wants to. Meanwhile, Eugene Wrayburn gets attacked and nearly murdered by his rival, Headstone. But Lizzie finds him left for dead in a river and saves him. The experience brings them closer together and they get married. Aww.
Falling Action
There is pretty much a blizzard of falling action in this novel.
John Harmon and Bella get married, and we learn that Mr. and Mrs. Boffin knew John Harmon was alive all along. Mr. Boffin was just acting mean and greedy to see if Bella would stand up to him.
In the meantime, Bradley Headstone (the guy who tried to murder Eugene) gets into a tussle with Mr. Riderhood, a guy who knows about the attempted murder and is trying to blackmail him. Both men fall into a river and drown.
Meanwhile, Silas Wegg steps forward to blackmail Mr. Boffin for his money, but Boffin informs him that the money is John Harmon's now and Wegg gets himself thrown into a garbage cart for his trouble.
Resolution (Denouement)
Now that the good people are married and the bad people are wallowing in their moral (or literal, in Wegg's case) filth, we look in on a dinner party where people are criticizing Eugene's marriage to Lizzie Hexam.
But one shy man named Mr. Twemlow finds the courage to speak up and say that if two people love each other, that's all that matters. The other people at the party try to shout him down, but it's too late. Love has spoken, even if the other high society types don't want to accept it.