When Dewey's pet rabbit does good in a state contest, the family must travel to Las Vegas for the nationals. But Reese unknowingly sells the rabbit to a restaurant. Now it is up to Dewey (with a little help from a "choking" Reese) to try and save the rabbit.

Meanwhile, Malcolm tells Hal and Lois that they embarras him, and that is why he didn't tell them he won state science honors. As a form of repayment, Malcolm gets great seats for him and Lois to see Lois' favorite singer. Lois then gets lucky and is invited backstage where all she really wants to do is figure out why Malcolm doesn't want her around.

Hal, on the other hand, is looking all across Las Vegas for a slot machine that he has had dreams of winning the jackpot on.

Francis is also in trouble when he gets behind on duties at the ranch, and for the first time sees that Otto isn't just a pushover for everything.

Malcolm gets a job working for Lois on the drugstore loading dock but is shocked to find that Lois smokes. She makes him promise not to tell, then turns her back on him and writes him up for a silly offense. Meanwhile, Dewey runs away to the Ranch to be with Francis because he says he is tired of Reese and Malcolm. Hal is also busy, secretly betting on and entering Jaime in baby competitions.

Malcolm gets his tongue pierced and needs to hide it for a month. While Lois' mother, Ida, comes and annouces that she will marry a rich Chinese Man that she met on a cruise. Malcolm gets complications when his tongue ring gets infected, rendering him unable to say "S's" and he discovers that Ida has been drugging her fiancé with opiates and mood enhancers. When Lois and Hal confront Ida, she drugs them with free food. But luckily, the fiancé misses a drug treatment, and realizes that Ida is a terrible woman and he leaves her at the altar. Malcolm is punished for his tongue piercing. Meanwhile at the ranch, Otto decides to hire a murder mystery acting troup, but it all turns out badly.

Reese continues to be a great soldier in the Army until he finds himself in a situation where his Sergeant cannot help. But after comparing being captured to being grounded, he takes action and leads his team to victory. But being such a successful soldier has it's bad parts as well, as Reese prepares to jump from the plane - right into Afghanistan. Malcolm has his hands full as well as he attempts to prove Hal innocent. But being good with numbers helps as Malcolm notices all of the prosecutions given dates are on Fridays - which Hal hasn't worked on in over 15 years. And with Reese missing and Hal's case, Lois falls deeper and deeper into insanity.

When Reese realizes the Army is too much for him to handle, he deserts and dresses as an Afghani woman. But Lois is on a march to find him, and travels to Kabul to hunt him down. Meanwhile, Malcolm volunteers at a veterans hospital as a way to make up for his guilt of making Reese leave.

Hal and Lois, strapped for cash, decide that Christmas gifts will have to be homemade this year. When everyone makes much better gifts than Hal, he spins a bigger and bigger lie about the present he has in store for them. In desperation, Hal pick-pockets Malcolm's secret credit card, and buys the family a ski vacation.

When Lois buys a brand-new king-sized bed, Hal thinks that her motive is to put more distance between them and refuses to sleep in it. Moved to tears by an opera he sees on television, Dewey is inspired to write his own operatic masterpiece, "The Marriage Bed," which is based on his parents' fight and turned into a school production. Meanwhile, Malcolm and Reese build their own street luge board; and Jamie falls head over heels for the baby girl across the street.

Hal is named executor of his neighbor's living will and must decide whether to keep him on life support or pull the plug. In attempting to make the decision, Hal discovers he is incapable of making decisions on his own because he always defers to Lois. Meanwhile, Craig asks Malcolm, Reese and Dewey to teach him how to fight dirty since a bully from his childhood is coming to town.

During Grandma's unwelcome visit with the family, she loses her leg while saving Dewey from a moving truck. Consumed with guilt, Dewey is determined to find his Grandmother's leg and give it the proper burial. Francis, on the other hand, begrudgingly becomes the caretaker for his stubborn, cranky grandmother. Meanwhile, Malcolm and Reese are given a new idea for a prank that forces them to stay awake days at a time to avoid the embarrassment of having their faces glued to the floor.

Reese befriends a pack of troublesome stray dogs; Dewey feels conflicted when he starts seeing another mother-figure; Hal unwittingly becomes a motivational speaker.

The family attends the counterculture Burning Man festival in the desert.

When Malcolm gets paired with a dimwitted beauty as his chemistry partner, he thinks it's a recipe for disaster, but when she reveals her feelings for him, sparks fly. They agree to keep their romantic experiment under wraps until Malcolm realizes that she's just embarrassed to be dating him. Meanwhile, Lois demands that Reese get a job, and she kicks him out of the house to prove that she means business.

Francis decides to surprise the family by coming home, and the power goes out in the house. Meanwhile, it's Lois who's in the dark when Hal decides to cancel their anniversary dinner in favor of a Reese-cooked meal at home. And Malcolm ends up in hot water after he sneaks three Dutch girls into the house.

Malcolm receives a check for $10,000. After Hal and Lois find out, they decide to keep the money and spend it on something for themselves. However, when Dewey overhears this, he wants to get in on it, too. Now, they'll have to find a way to pay Malcolm back.

Lois, Hal, and Dewey go out of town for a piano competition, so they get Ida to watch over Malcolm and Reese while they're gone. Since Ida thinks Reese needs to become a man, she comes up with a competition for Malcolm and Reese, and if Reese wins, he can take Raduca as his bride. Now, when Lois and Hal return, they're surprised to find out that Reese has run away to Las Vegas to get married.

Hal's friend Trey tells him to come to his dental office when he looses a tooth during a poker game, but their friendship becomes in jeopardy when Hal's faced with a $2,000 bill and causes a fight between them. Reese, meanwhile, teaches Lois how to ride a bike, while Malcolm and Dewey find sleeping as their new favorite pastime.