Robbie and Mary get to go to the movies on a double-date with his brother Rick and Lucy, but that unwilling couple ends up cheating on their partners, while Robbie has another secret. Simon and Nigel buy cigarettes illegally for a school project, yet Eric waits even while they ponder about smoking 'just one'. Matt is a wreck after Shana fails to call once, worse when she does too cheerfully, but his very despair attracts both girl neighbors his house-mate invited.

The parents insist on spoiling the kids' Valentine's day by celebrating the baby twins' birthday and demanding presents. Robbie gets permission afterward to drive Mary to the coffeehouse where his parents met. Matt puts off telling Shana his ex Heather transferred to his college, but Mary spills the beans. Simon's first passionate kiss caused a love-bite, which Deena meanly insists to return, causing disastrous discovery. Matt sees Robbie with 'his brother's date', sees through it but isn't believed that's cheating, until the romantic trip's hidden agenda is revealed.

Each one of the Camden kids has a relationship problem; Mary decides to skip college and get back together with Robbie; Simon is dumped; Matt is torn.

Simon learns the truth from Deena about why she broke up with him; Ruthie and Lucy try to reconcile with their exes; Matt gets back together with Heater.

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.

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 wonders why Matt is suddenly so friendly, ignoring it's because Matt dates his ex Cheryl, who wants him to tell Robbie but doesn't push that, while Robbie spontaneously tells he studies a course with Heather, who needs his help. Simon feels a social outcast when nicknamed 'virgin Camden' because his mother assured Sasha's blabbermouth ma he's sexually inactive, but actually schoolgirls line up to date him. Viciously jealous, Annie meanly forces Eric to give up counseling Serena, yet denies that's her doing and sticks to her guns after Ruthie commends her as bitchy selfishness-model.

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.

Robbie amuses sneaky cookie-thief Ruthie by nicknaming her Snookie and sets straight Lucy's far less flattering interpretation. Wilson diplomatically handles Mary's absurd blaming him for her failed fire department application after she set fire to the colonel's curtains. Despite Eric's continuous meanness, Simon acts most responsibly when a kid only he, not even a teacher, defended against school bullies mentions planning to shoot them. Eric confronts the supervisor of a firm's staff where 'pranks' extend to stealing a prosthetic arm an counsels his ex Merle on forgiveness.

Insecure Robbie hides his budding rebound-affair with Lucy. Wilson is deeply hurt when he finds fickle 'bride' Mary kissing fire-department coursemate Ben Kinkirk. Simon doesn't enjoy bully-mate Rick's girl abusing him as excuse to dump him. Annie's flippant advice nearly wrecks pupil Christy Parks' parents' marriage, yet she resists help even from Eric.

Robbie and Lucy gather the courage to tell everybody about their affair, only to find they all knew and don't really care. Without the thrill of sneaking, their first date fizzles. Ben Kinkirk and Mary both pass the firefighters course, but their meeting on whether to celebrate with classmates messes up Mary's reconciliation with fiancé Wilson., and Billy's questions make Wilson decide against her plan to elope. Matt discovers that Hank and Julie are planning a divorce, and Eric and Annie try to find out why and see if they can help fix it.

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.

Eric continues his apathetic ways, and it gets to the point where Annie insists he see someone to talk about it. Cecilia starts avoiding Simon. Ruthie learns a friend has cystic fibrosis.