The family goes to the zoo. Malcolm is going through a crisis, and he and Dewey find themselves in a unfortunate situation. Reese angers an animal at the zoo. Hal is jealous of a former flame of Lois's who works at the zoo.

In a desperate attempt to get rid of his Krelboyne past and start afresh, Malcolm ends up making things even worse than they were.

Malcolm and his family goes to Hals father's house for a reunion. The family doesn't like Lois. Reese and Dewey try to get in their grandfathers will. Malcolm's grandfather takes a special interest in him, while the young cousins love Francis.

Malcolm stops thinking in order to go out with a very dumb girl. Hal wins some money, and rents a steamroller.

Today is Malcolm's birthday and unfortunately he and Reese are in a long prank war against each other. Meanwhile Francis does battle with a legend about an evil cow at the Grotto Ranch and Hal is forced to enlist Craig Feldspar to help him with a comic book present.

Malcolm sneaks around to date a girl whose father hates him; Hal and Lois become more productive when they can't have sex for a week; Dewey discovers he's an "evil twin"; Francis mediates a dispute between Otto and his cowboy neighbors.

Malcolm is fed up with the fact that every time he complains, something wrong happens. He has recently got kicked off the basketball team and vows not to complain anymore. He receives good results by not complaining - he gets back on the team, negates Lois' anger by not talking back to her, and gains the respect of his girlfriend, Nicki, who shares a kiss with him. Next, Hal decides to be a speed waker and soon gets competitive with a local walker. Meanwhile, Reese wants to take Alison to a concert and the only driver he can find is Craig Feldspar. However, Craig has plans of his own for his two passengers - a hay ride and a bonfire dinner. Alison is fed up and pepper sprays him and threatens to give Reese the same treatment if he doesn't let her go her own way. He's pissed off as Craig plays his ukulele and sings a song from Air Supply.

On a visit to Francis' dude ranch Hal can't help being disappointed in Francis' success, Reese and Malcolm fear Francis has turned into an overly responsible grownup, and Gretchen punishes Dewey for breaking a valuable doll.

When Lois' mother visits, she trips on a leaf and decides to sue Hal and Lois...just as Lois finds out she's pregnant again.

Lois fantasies what her life would be like if she'd had girls instead of boys.

Lois uses a long drive with Malcolm to further his sex education; Reese spends a day in prison; Dewey plants seeds of discontent in Hal's vocal group; Francis has an accident branding Otto's favorite cow.

When Hal kicks Malcolm out of the house for misbehaving, Reese tries to take advantage of Hal's distraction to come up with a truly bad stunt of his own, and Francis takes offense when Otto's musician nephew plays a musical accompaniment to Francis' every move.

Hal lands a second job at an electronics store, while Malcolm is dumbfounded by their new babysitter, who's the same age as himself.

Hal spends a wild night with an old high school buddy; Malcolm tries to liberate Dabney from his mother's control; Francis spends the night with Otto when their wives are out of town.

The family decides to hold a garage sale to fund repairs of the bedroom wall and Lois puts Reese in charge. Hal finds his old radio-transmitter and starts running a pirate broadcast like he once operated in college.

Malcolm competes in an academic octathlon but hates the intensity of the other competitors; Hal fights to regain Dewey's love; Reese tries to get out of going to a formal dance; Francis and Piama's argument over chores proves highly contagious to other couples.

As Lois and Hal write their wills in preparation for the baby's birth, they recall various colorful incidents with their four current children.

When Hal and Lois go on a less-than-romantic getaway, Reese throws a party at home, which is crashed by delinquent friends of Francis, who take over the garage and hold the boys hostage.

Malcolm meets a chess-playing bum who could be him in 30 years; Lois can't figure out why she's gaining weight; Dewey attributes his bizarre behavior to obeying requests from the fetus Lois is carrying; Francis objects to Piama posing nude in an art class.

Hal takes the boys to a bridal show; Lois' mother wants to move in with the family; Malcolm gets an offer to enroll in a prestigious private school.

Lois continues with her strenuous labor, as friends and family all panic around her.

The family joins a church in order to take advantage of the free day care; Francis concocts a UFO story to help the dude ranch.