Robbie and Cheryl ask Eric to marry them because of her pregnancy. He smells a rat and learns just in time that she intended to trick Robbie, who is grateful to escape a loveless marriage and offers to stay away from Mary. Lonely Simon has joined punk Norton's schoolmates gang. Lucy, who is lightly butt-slapped, and the Camden parents, make huge scenes over inappropriate remarks from some of the knaves, treating Simon as if he 'hates women'. Matt tries to help both sides understand, but fails, yet a real incident shows Simon's truly good nature. Matt can go for Priscilla after hearing from Heather she's dating another already.

Robbie's ma lost her house and moved away without him and moving in with Cheryl also fell through, so Eric finds him studying outside, yet keeping up top marks. He promises to find a shelter and takes him home meanwhile. Despite embarrassing episodes, all the fault of Camden girls, Robbie proves himself a model house-guest. So Matt finds the couch occupied when chased from his dorm by John, who is completely besotted with Priscilla Carter. Simon keeps is foxy new date Sasha a secret until she arrives in a BMW. Lucy is passively jealous when Mike Pierce announces he got early college acceptance, then goes over to make up and thus discovers his ma's disabling mental condition.

A month later, perfect house guest Robbie is getting popular with most Camdens, except Annie who childishly splits hairs about his domestic input, meant to help her but making her feel redundant, while Ginger takes care of grandpa. Matt is unwilling to stand by John when he meets the Carter parents and seeks refuge with Heather, whose boyfriend Thomas gets them off their backs by suggesting they're a sheets magnate family. Mary starts a round of panicking with a false rumor that Robbie is dating Lucy. Simon is flattered when Robbie asks his financial advice and starts copying him, even Matt follows suits walking around shirtless. Robbie finds a surprising job and the perfect thank you gift.

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 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.