When the Wilkersons came back from their vacation they found out that the whole block was making a huge party to celebrate that they were gone. While Lois and Hal join a sausages-eating contest, Reese and Dewey start to make money by torturing younger boys and Malcolm, without knowing it, helps a thief to steal everything in the garage of an innocent family.
Malcolm is a regular high school kid trying to navigate his way through life despite the various obstacles thrown in his way a complete misunderstanding of girls, the constant burden of masterminding plans to get himself and his brothers into or out of trouble, and a miserable job at the Lucky Aide not to mention a severe case of teen angst.
Although Malcolm has a genius IQ, he can't seem to make sense of the opposite sex, much less his embarrassing family. Lois is the outspoken, opinionated mom, who still manages to rule the roost even though her boys are growing wise to her crafty ways. Hal, a dad who is just a bumbling, big kid at heart, often finds himself creating more chaos than his five boys combined.