In a town there is a Miller that has a wife and a little son and young, not-so-lovely daughter. He's known in his lands to cheat his customers of grain and two young scholars, Allan and John, promise to outsmart Simkin, the Miller. They bring grain to be milled to Simkin who immediately deciphers their MO. He decides to outsmart them in return and slips away unnoticed while the two young men keep a watchful eye on the milling process. Simkin releases their horse to the fields and when the men's grain is finished, they discover their horse is gone. Both men abandon the original grain-observing mission to scour the countryside for the horse. After capturing the horse it's night and Simkin let's the young men stay the night for a price. The home is very small and so everyone sleeps in the same room. Disgruntled by being screwed by the miller, Allan decides to screw Simkin's daughter and slips in her bed. John ends up doing the same but with his wife and when dawn comes, you can imagine what a scene that was. Here's the end of the Reeve's revengeful tale (verses 396-404) where the Reeve gets his final word:
396 Of Alain, and of John, who've tricked him well.
397 His wife is taken, also his daughter sweet;
398 Thus it befalls a miller who's a cheat.
399 And therefore is this proverb said with truth,
400 An evil end to evil man, forsooth.
401 The cheater shall himself well cheated be.
402 And God, Who sits on high in majesty,
403 Save all this company, both strong and frail!
404 Thus have I paid this miller with my tale.
Don't you love how the personalities of the pilgrims like Oswald (the Reeve,) come out in their tale-telling? Okay, we get it, Oswald. You don't like the Miller.