Robbie is not amused by week-long roommate Matt's jealous whining, but still helps him make up with John, who lacked the courage to tell Priscilla her 'Japanese' room remodeling disgusts both guys. Mike decides after a kiss without chemistry to trade in Lucy for Elaina Casey, while matching Lucy with Mike's friend Jeremy. Simon and Robbie prevent suddenly jealous Lucy's reactions spoiling the whole partner-switch, which thus ends well.

Everyone but Lucy is stuck home celebrating the twins' birthday on Valentine's Day; Lucy and Jeremy keep running into Lucy's ex-boyfriend.

Robbie is told last, despite Camden's advice for her to be open, that Mary has bumped into her ex Wilson, who does a course in Buffalo, and agreed to a dinner at his place. Robbie is doubly vexed as he immediately calls her after meeting a lookalike, Marie, also a basketball player, whom he asked over to get hold of her study notes. Matt meets and dates Cheryl before he realizes she's Robbie's ex. Mary also bumps into Lucy's Jeremy.

Robbie panics when Mary announces she's returning for the summer months, so he tells her to follow parental instructions not to date her all that time. Mike inspires Lucy how to stay with Jeremy now he's accepted to Juliard: marriage, so they get engaged. Matt is dumped by Cheryl for not telling the family about them, but that gives him the courage and more reward then he bargained for. Wilson was dumped but traveled all the way home, just when Mary's claim of sexual intimacy with Jeremy make Robbie deck Lucy's equally startled fiancé. Simon and Tim discover Deena dated each of them behind the other's back. Serena abuses her lonely birthday to make a move on therapist Eric, while hardware shopkeeper James Carver courts long-oblivious Annie.

Robbie gathers the courage to tell Mary openly, now her lies are exposed, their relationship is over, staying with the family his priority. Simon nurses his broken heart on account of Deenah, refusing to become 'just friends' again. Wilson bonds, while bunking, with Matt and Robby, and demands for Mary to return and go steady in New York, or break up completely. Jeremy forgives Lucy for doubting her fiancé's fidelity. Ultimately Eric helps her transfer to his New York alma mater, near Juliard. The Camden parents finally realize Serena and James are seducing them, ward off each suitor and match the lonely hearts.

Simon's big day, the start of his driving lessons, finally arrived, but Eric just forgot about it. Grandpa Jackson seduces the knave into driving him around without a license, which leads through more bad grandfatherly advice to a televised police car chase. Jealous of Joy, Matt behaves childishly toward Robbie whose gentleman's attitude ultimately gives in. Lucy hoped Jeremy called to make up, but he just wants his engagement ring back. The local fire chief isn't fooled by Mary's eagerness to transfer.

The next Valentine's day, Robbie prepared a surprise for Joy. Mary meanly supposes the hotel she overheard him contacting by phone means another sex trap. Joy, who assumed the butler to be away like her father really is, isn't discouraged, but bitterly claims Robbie doesn't love her truly because he refuses to risk getting intimate. Matt contacts all his 'true lovers', wondering why he never stayed hooked up. Lucy again assumes Jeremy, who is back in town and double-dating with Mike, wants her back and pretends to have a date. Mary is shocked to see Wilson moved back and goes steady with her former school friend Corey Conway. Simon gets permission to let his hot senior date Maria 'help babysit' and gets her cute kid brother Jake to spare Ruthie dateless embarrassment.