Two naïve young clerks think they can easily get the better of the miller who cheats all his customers. They propose to their headmaster that they be allowed to take a trip to the mill to watch their corn being ground, and brag to all their friends that they will achieve success where older and wiser people have failed. Little do they know that getting the better of Symkyn is harder than it might first appear.
The two clerks are jovial and care-free when they arrive at the mill, thinking they've got everything figured out. One clerk proposes to watch the corn as it goes in the hopper, or grinding mechanism; the other will watch it when it comes out. This way they'll guarantee that Symkyn doesn't cheat them of corn, right? Everything seems to be going perfectly for these two.
The clerks have no choice but to chase after their horse, despite knowing that their absence from the mill will give Symkyn the perfect opportunity to steal from them. Catching the sexually-excited stallion proves to be extremely difficult, and by the time it's over the clerks know they've failed at protecting their corn. Not only that, but it's gotten so late that now they have no choice but to spend the night with the devious miller, giving him more opportunities to cheat them.
The nightmare in question here is actually for Symkyn's wife and daughter, as the two clerks sexually assault them. When the large and aggressive Symkyn awakes, however, John and Aleyn are in serious trouble.
The clerks manage to defeat the "monster" in the form of an aggressive and enraged Symkyn, whom they leave unconscious on the floor of his house. Making their exit in a hurry, they pick up their stolen corn thanks to some information from Symkyn's daughter, Malyne. Having fulfilled their boast after all, John and Aleyn will have a happy homecoming.