Before vaccines were widely available, life-threatening illnesses were just another part of childhood.
They're so much a part of life that Mamma has a system for dealing with them: She uses the first child infected to get all the boys sick at once so when they're all better, the family is done with the terrible illness du jour.
Mamma's system is a real problem for J.D. because, for whatever reason, he never gets sick first, so he never gets the chance to feel better first and make fun of his brothers for still being sick.
After a bout of the measles, which S.D. gets first, J.D. decides he's going to be first for a change, and when his friend Howard Kay gets the mumps, J.D. sneaks through the quarantine to get infected.
It takes the mumps a while to show up, but when they do, he's thrilled. Finally, he's first at something.
Since he can't contain his glee, his family figures out what's up.
After he recovers first, according to plan, he rubs it in Tom and Sweyn's faces. He's having a grand old time, but then they turn the tables and declare he's getting the silent treatment from them for a month.
J.D. can't stand this and promises Tom he can have anything he wants if he and Sweyn will lift the silent treatment.
Tom has been eying the real Indian beaded belt J.D. received from Uncle Mark for his birthday this whole time, and he convinces J.D. to trade it for the end of the silent treatment.
J.D. reflects on what a wonderful, generous brother he has, and we reflect on the fact that J.D. is not the sharpest knife in the drawer.