Pamela is the 15 year old handmaid of Lady B–. When her beloved mistress dies, she becomes the servant of Lady B–’s son, Mr. B–. Mr. B– takes what you might call an ungentlemanly interest in Pamela. Not to put too fine a point on it, he tries to rape her. Repeatedly. Pamela is well liked and respected by the other servants, whose intercessions on her behalf cost them their jobs. Lady Davers, Mr. B–’s sister, also disapproves of her brother’s conduct, although less for Pamela’s sake than for her own pride, as Mr. B– condescending to a servant would disgrace the family.
Having thwarted all of Mr. B–’s attempts, Pamela is at last dismissed and sent home to her parents, only this too is a ruse. She’s actually taken to another of Mr. B–’s estates and kept prisoner under the close watch of Mrs. Jewkes. The attempted rapes continue and grow more violent. Pamela contemplates suicide. The local minister secretly tries to free her but his plan is discovered and Mr. B– has him jailed.
Seeing that the matter can’t be forced, Mr. B– instead tries to buy Pamela, offering her a sizable estate and yearly allowance in exchange for being his mistress, but Pamela rejects this even more vociferously. So greatly is he offended at this slight to his largesse that he declares he’s finished with Pamela and sends her home for real. After she’s gone, he realizes that he really, truly loves Pamela. He recalls her and they marry. Pamela is eternally grateful to her most good and generous master. Even more so when she learns of how lately repentant he is of that affair he had with Sally Godfrey and the resulting “niece” that he still won’t own.
Pamela is generally termed an epistolary novel, but that conceit is dropped fairly early on. Most of the book takes the form of a diary, and even then, it’s only a diary because Pamela once in a while reminds you that that’s what her first person narration is supposed to be. A couple times, Richardson abandons even this and drops into omniscient third person.