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
The Age of Innocence
When we meet Pamela, she's a sweet, pious, innocent teenager who is as heartbroken that her mistress has died as you would be to find out that One Direction broke up. (We kid!). She's initially worried about keeping her job, since her sole purpose was to be the lady's waiting-maid; however, Mr. B, the new master of the house (and the son of her late mistress) agrees to keep her on.
Woohoo! Now we're all set up with the need-to-know info: the main cast of characters and the event that changes the protagonist's static state: Pamela's embarking on a new adventure as the servant to a sexy single man.
Rising Action
Not That Kind of Master
Unfortunately for Pamela. Mr. B takes a shine to her. He harasses and attempts to rape her, but Pamela manages to escape (though not without severe psychological trauma). This phase of the book is chock full of arguments and attempted violence, which means lots of conflict/complication.
The main conflict here, though, is between Pamela's modern individualistic moral code, which involves protecting her honor a.k.a. virginity, and Mr. B's old-fashioned aristocratic moral code, which thinks of servants as basically the property of their masters. Guess who's going to win? (Hint: you don't see too many aristocrats blithely raping their servants these days.)
Climax
The Great Escape
After lots of near misses, lies, and escape attempts, Pamela has some kind of bad fit after Mr. B sneaks into her bed and attempts to force himself on her. The incident seems to touch off a major turning point for Mr. B, who resolves not to force himself on her and even claims to be falling in love with her.
When she doesn't get as swoony as he would like at these declarations (imagine that), he's furious and boots her out of the house… until he writes and begs her to return. Impressed by the turnabout in his behavior, Pamela agrees. Turns out, she loves him too! This moment, or series of moments, represents a huge 180 for both characters. It's the climax of their will-they, won't-they relationship, when they figure out that they will.
We've known it for a while, but then we're spoiled by over 200 years of reading and watching plots based on Pamela.
Falling Action
Mr. and Mrs. B
When Pamela returns to the Lincolnshire house, she and Mr. B get married. Yay! Throw the bouquet in our direction, Pam!
But before she can enjoy being rich and married, Pamela has to contend with her mean-girl sister-in-law, Lady Davers. While Lady Davers is disturbed to hear that her brother has been brutalizing his servant, she's even more upset to think that he might have married her. After extended confrontations between Pamela and Lady Davers and then Lady Davers and Mr. B, everyone makes up, and Lady Davers accepts Pamela as her sister.
So, there is still a fair amount of conflict going on here, but this section of the book is really about Pamela settling down into married life and dealing with the fallout of her class elevation—and that's falling action if we ever saw it.
Resolution
Happy Ending
Pamela and Mr. B return to Bedfordshire, where Pamela wins over all the local gentry, dispenses some of her new-found wealth to the poor, and sets a good example for Mr. B's illegitimate daughter. See, ladies? Just find yourself a nice abuser and you, too, can live the dream.