Lois must take drastic steps to discover which of her sons ruined the special dress she bought for an anniversary dinner with Hal.

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.

While Hal secretly takes the boys to the stock car races, Lois desperately searches for her missing paycheck. Francis at military school is keeping a boa constrictor as a pet.

Roller-skating lessons from Hal bug Malcolm, who rebels against dad's discipline while mom agonizes in bed from a backache she blames on Reese. Francis avoids his squad's survival weekend.

Malcolm and his Krelboyne classmates enlist the help of Hal for a school project, which involves a robot, and an enormous swarm of bees. Lois visits Francis at his school after he becomes injured and soon clashes with Spangler.

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

Malcolm's humiliation as a Krelboyne drives him crazy, so he fakes his way into seeing the school's shrink, with whom the con continues.

Dewey starts carrying a purse to school. Francis's friend Richie joins him at military school. Malcolm becomes a slave to an old woman in the neighborhood.

Lois' estranged parents, Ida and Victor, pay the family a visit. Right away, trouble starts brewing. Victor bonds with Reese, Ida gets Malcolm into a fight, and Dewey is haunted by childhood memories of his inattentive grandparents.

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.

Lois forbids the boys to ride a motorbike they found, but Reese disobeys and breaks a leg.