Plot summary
When Stevie finds out his mother has divorced his father, he falls into a depression and Malcolm tries to cheer him up -- and ends up in trouble for bullying and mocking Stevie's disability. Lois' high-school diary falls into Reese's backpack and he reads it and becomes infatuated with the diarist – and is horrified to find out her identity. Dewey regresses into babyhood, appalling Lois. Meanwhile, neither Francis nor Otto can bear to kill a horse having a deadly infection; they nearly kill each other in trying.
Credits
Adapted from Wikipedia contributors, Malcolm in the Middle season 5. HTML formatting and reference markers removed.