In the scene before the credits Lois asks Hal whether he has baby-proofed the kitchen. He assures her he has. We then see Jamie opening a kitchen cabinet, only to be scared off by Reese who's hiding inside.
Malcolm and Reese are bored and sort of blame it on Stevie, who limits their activities. Stevie seems to be happy reading a magazine on extreme sports. Malcolm notices an article about street luges and gets very excited about it, though he hides it from Stevie.
Hal is irritated by the fact that Lois bought a new bed, a bigger one than before. He suspects that she's trying to keep a distance between them. Jamie spends most of his time staring out of the window, looking at a female toddler across the street. Dewey tries to fight his boredom by watching television. He gets completely bowled over by an opera and decides to write his own. If only he could find a subject...
Malcolm finds out about local street luge activity by logging on to a street luge chatroom. When Reese and Malcolm take their self-made luge board to the steep hill, Reese chickens out. Malcolm is prepared to have a go, but he quickly gets pushed off the street by a mysterious luger in a dark helmet. He decides to improve the board.
When Hal and Lois fight once more about the bed, Dewey realises he has found his subject for the opera. In his mind the argument turns into a mass spectacle. Later on he has his classmates play out his composition. He quickly comes to understand that he hasn't got a satisfying resolution for the conflict/opera though. Meanwhile, Malcolm keeps rebuilding his luge and keeps crashing it.
When Hal notices that Lois moves away from him during the night, he takes that as proof of his wife's growing coldness to him. After a while, Lois admits there is a problem. At the end of the day she suffers from gas. If she releases it during the night, Hal shouldn't be too close. To her surprise, Hal is not shocked. He tells her she has been farting in bed every night of their marriage. He's used to it. Hal and Lois are so relieved that they kiss and make up, giving Dewey the final act for his opera.
Malcolm believes he has created the perfect luge board and he dares the mysterious luger to a race. (To make sure that he'll win, he arranges for Reese to jump out of the bushes and scare the other guy during the race.) The plan fails when Reese is shocked to see the mysterious luger lifting his mask. It's Stevie! Confused, Reese steps out of the way. With the help of the jet propulsion of his inhaler Stevie wins the race, but he accidentally drives onto a trailer truck and is propelled into the air, hitting a tree. Little Jamie has a bad day as well: he notices a little boy staying with the little girl across the street.
The family goes to Dewey's school to see the first performance of his opera. Lois hopes Dewey won't make a fool of himself, not realising that her son will soon tell everyone her embarrassing secret.