Dewey's placement in a competition gives the family an excuse to take a trip to Las Vegas. While Hal tries to find his dream super jackpot slot machine, Lois makes time with a lounge singer.
When the men offer to take care of the baby to let Lois catch up on rest, things fall apart. First, Hal leaves to get diapers. Then Malcolm, Reese and Stevie take off after a trio of girls which only leaves Dewey behind with the baby.
Stevie's parents are getting a divorce and Reese lets Stevie know this. Stevie has more than just a little difficulty processing the information. Reese processes a mystery girl's diary only to be weirded out when he learns it's his mother's.
Malcolm chooses a party over Thanksgiving with his family. Reese becomes tyrannical in his dinner preparations. Francis and Piama arrive in the middle of a fight.
Malcolm decides to place a hidden camera in Reese's bedroom as his study of a deviant mind at work. Dewey skips out of school to work the streets as a street performer. The Grotto receives a very negative newspaper review.
Lois hooks Malcolm into a Lucky Aid job. Malcolm catches Lois smoking at work. Hal's participation in a "Father and Me" class becomes an all-out rivalry amongst the dads. Dewey checks in on Francis at the dude ranch.
Hal and the boys run a Christmas tree lot but run into stiff competition from a local church.
The family returns from vacation to discover the neighborhood block party is going on. Malcolm absentmindedly assists a burglar in an attempt to keep away from his family. Hal and Lois go mouth-to-mouth in a kielbasa eating competition. Reese seeks money even at his own personal expense.
Hal flirts with the person in his office that manages cutbacks. Malcolm takes on the school's censorship of the school literary magazine.
After not maitaining his hot tub as promised, Hal develops a rash. Malcolm takes a step towards adulthood in gaining his driver's permit.
Grandma Ida comes to visit and lets the family know she's planning on marrying an old Chinese man and moving to China. Malcolm's tongue piercing seriously stunts his vocabulary.
The pressure Lois exerts over Malcolm makes him an awful player for the Lucky Aide Softball Team. Lois drops him for another player. Reese decides to one-up Francis by stealing more toilet seats from the junkyard guarded by dogs.
Lois's sister Susan arrives in town in need of a new kidney. Susan has always had hard feelings over Lois taking Hal from her.
Malcolm feels closer to a girl he's dating when he finds out how similar their families are. Lois tries to take down a pizza place that's repeatedly made her pay too much in the past.
Francis takes umbrage when Hal and Lois kick Reese out of the house. Malcolm tries to help a football player with his college essay.
Malcolm's college visit is cramped by his tag-along mother. Lois goes head-to-head with the dormitory resident advisor. Reese poses as a drug dealer to get the attention of a pretty undercover officer.
Hal and Lois each set babysitter Polly up with a guy and then ask her to choose between them even as the two men prepare to come to blows. Reggie Jackson mediates a fight between Malcolm and Dewey.
Dewey's attempt to sidestep the potential ridicule of becoming a Krelboyne student backfires when he does so poorly on an IQ test that he's sent to be a "special" student. Dewey decides to take control of his challenged classmates and lead a rebellion. Hal and Craig compete on a dance video game.
Reese's fussing with Malcolm and Stevie's chemistry experiment gets it to work, but then he can't figure out how he did it. Dewey tries to increase his candy sales by lying.
Lois discovers that her father's secreted Canadian family is remarkably idealized considering how similar they are. Ultimately, Lois learns that her father wasn't really her father.
Hal finds himself under house arrest when he refuses to air an FBI investigation. Reese joins the Army under an assumed identity after catching his girlfriend and Malcolm together behind his back.
Hal tries to impart some knowledge to his boys as he believes he's about to be jailed. Malcolm hopes that something his father told him will ultimately set Hal free. Lois buckles under the stress of all that is happening to her family. Reese succeeds at boot camp because of all of Lois's pressuring.