Malcolm's cushy babysitting job provides relief from the trailer the family's using while their house is being fumigated, until Malcolm learns that the trust placed in him in his new position is strictly limited. Meanwhile, the military school's master key leads Francis to a corpse, for which he provides a proper send-off.

The boys stay home from school when their mother thinks it's Sunday instead of Monday. Malcolm thinks of a plan to get Francis out of trouble once again. Hal gets sucked in by a Porsche dealership.

Shenanigans abound at the fancy spot where the family's dining with the Kenarbans, and at Francis' school, where rowdy teenage girls are partying.

Hal and Lois heads off to a convention while the boys stays home for the babysitter. Malcolm, Reese and Dewey assumed it's just another old woman, their parents hired to watch them. They decide to do a series of pranks on their babysitter, which includes the covered up sewer tank with a blanket and a book for the old woman sit on. To their surprise, their babysitter is a hot, teen-aged girl named Patty. She is sweet to them, but also bitter because she was rejected by Francis, a long time ago, because she was obese. Now the boys compete against each other to see who will prove their eldest brother wrong in his rejection and sleep with her without sex. Meanwhile at the convention, Lois tries in vain to stop the fight between Hal and Jack, who stole his idea.

Malcolm gets a role in the high school play and is so captivated by high school gossip that he forgets his lines. Lois discovers the joys of massage. Hal and Dewey build a society of model buildings in the living room. Francis tries to show his individualism at school when the commandant cracks down on personal belongings.

Reese, promising champion of his school's wrestling team, gets beaten by a girl, completely demoralizing him. So he gives up his school-bully carrier, which destabilizes the natural order of things at school. Francis tries to get out of academy at his birthday in an attempt to avoid academy-birthday-traditions.

Lois gets a traffic ticket and immediately blames Francis and makes him get the money to her. To do this, Francis stages a stunt for the other cadets' amusement. Malcolm finds evidence that Lois was wrong about the traffic ticket.

A hospital stay unsettles Malcolm, who's stuck in a kids ward with what may be appendicitis. Meanwhile, at military school, Francis leads a hunger strike.

A cooking class energizes Reese; a planned party irks Malcolm, whose brutal honesty hurts the hostess, Krelboyne Cynthia.

Lois is two weeks late with her period, causing her and Hal to panic and start a big fight, while trying to keep it from the boys. And while Dewey is scared that his parents may split up, Hal and Lois remember the troubles of getting their previous four sons.

In an effort to contribute to society and to make her boys useful at the same time, Lois "volunteers" Malcolm, Reese and Dewey for charity work at a local church. The boys are assigned to sort giant piles of donated clothing, game, appliances etc. Initially irritated at their new task, they realize the donated stuff is a lot nicer than their own possessions, and they begin swapping out their old stuff with the second-hand items. The boys soon make a enterprise out of their charity assistance, going as far as to sell things to the neighborhood kids - that is until Hal finds out. Meanwhile, Francis must come to grips with the fact his fabulous job in Alaska is not quite what he expected.

When Malcolm and his brothers destroy their Christmas tree ornaments, Lois punishes them by canceling Christmas and moves all the presents into the garage. The only way she will reinstate the holiday is if the boys behave impeccably up to Christmas morning. Her plan works better than expected, and Lois is touched that her family responded so well to her challenge. Meanwhile, the boys decide that Lois could use this tactic for future holidays and retaliate by breaking into the garage and opening up all the presents. Elsewhere, Francis is forced to visit his Grandma Ida for Christmas.

A negative job-performance review riles Lois; hoops play with the boys energizes Hal; a vermin infestation busies rat-killer Francis.

Highway horror: Reese gets a learner's permit, which he promptly proceeds to abuse by commandeering a driving-school vehicle.

Clever Hal invigorates Dewey's soccer team; sly Reese blackmails a philandering neighbor; obsessed Malcolm battles a computer program.

Girls in the house spell trouble for the boys, who are on their own while Dad's hosting a poker game that's more about one-upmanship than cards.

Back in the general school population, the Krelboyne whiz kids wind up in cliques with jocks, skateboarders and brooding "Goths."

High school's first day vexes Malcolm, who acquires an unfortunate nickname; and Hal, a parental "volunteer" running afoul of authority.

After joining the basketball team at school, Malcolm soon finds himself under the coach's skin due to his constant complaining, which eventually gets him kicked off the team. Determined to put an end to his horrible habit of talking before he thinks, Malcolm starts "holding his tongue" which solves all the problems with his coach, girlfriend, and parents, but it ends up causing more stress than before. Meanwhile, Hal takes up speed walking and is desperate to be the best while Reese gets Craig to take him and Allison to a concert and almost ruins his date.

After Lois is out of town, Malcolm and Hal got into a fight leading Malcolm to get expelled from his house. Malcolm lives with his girlfriend in her attic, as Hal put signs for "Missing Malcolm."

Malcolm tries to emancipate Dabney from his overbearing mother while Hal invites his ne'er-do-well old buddy to the house. At the ranch, Francis is forced to share a room with Otto.