Plot summary
While Hal and Lois are away for the weekend, Francis comes home from military school to babysit. Malcolm overhears a discussion between Lois and Hal's about Francis out of context, and believes he will be allowed to return home permanently if he watches over them well enough, so Malcolm convinces the other boys to be on their best behavior. A series of reckless behavior nevertheless occurs, but the boys manage to fix and hide all of them in time. Seeing the good work Francis has done, Hal and Lois send him back for military school, on account of how much they think his behavior has improved since going there.
Credits
Adapted from Wikipedia contributors, Malcolm in the Middle season 1. HTML formatting and reference markers removed.