When Hal's doctor discovers something suspicious during his routine check-up, Lois and Hal become frantic, nervous wrecks as they wait for the test results. As a result of her anticipation, Lois becomes even stricter with the boys, leaving them to misinterpret the new house rules. Meanwhile, in Alaska, Francis comes to blows with his boss.
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.