Acting dumb like Reese eases Malcolm's stress and lands him a date with the new light of his life, an attractive girl who's really a dim bulb.

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.

Jessica, a sly, 16-year-old sitter outfoxes the boys while Lois is away and Hal's busy with a second job as a whiz of a salesman.

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.

An academic competition faces the Krelboynes in an event Malcolm derides. Especially when he learns his teacher has a cheating plan. Also: a commitment to a formal dance ruffles Reese, who's now trying to ditch his date.