After Simon's school project volcano is carelessly ruined by brainless Ruthie, it's time for him to move to his own room. He's less happy with the isolated attic he's supposed to go to, but Matt agrees to move there and hand over his room, eager to 'move' to an out of state college anyway. Wilson calls Mary, but only to babysit Billy while he takes his date to her prom. Despite home advice, Mary performs miserably, yet Wilson returns early, having decided he only wants a girl who tells he family about Billy. Lucy desperately recruits enough big sibling support to get permission to go eat in town with two 'cool' sisters. Being driven in their car is forbidden, which turns out to be a life-saver, alas literally, leaving a guilt problem.

Simon invests in a babysitting course, but pays dearly when he lets Annie talk him into trying out on Ruthie, who already abused every older sibling even when much younger. Matt desperately seeks inspiration for a college project on sexuality. Jordan patiently handles Lucy's insanely jealous and insecure worries after a -for him, unlike Mary, canceled- senior jocks sleepover until Matt comes to her 'rescue', then spontaneously braves Eric. Annie befriends pregnant teenagers in her infant care class.