After their lackluster attempt at kissing, Mike (guest-star Jeremy Lelliot) and Lucy agree to be friends and to fix each other up on dates--- but the plan bothers Lucy more than she anticipated. Meanwhile, Matt's in a huff over John and Robbie's newfound friendship and feels slighted by the family. Eric also continues to feel alienated from his family when they keep going to Annie for advice. Also, Annie feels slighted when Ruthie plays an un-funny joke when the twins recognize her as their ""mama"".

Mary's feelings for Robbie resurface when she inadvertently finds out he has a secret date for Valentine's Day, and the whole family schemes to uncover the mystery woman. Meanwhile, with the exception of Lucy who has a date with Jeremy, the other Camden kids feel deflated when their Valentine's plans fall through and they end up stuck at home celebrating Sam and David's second birthday. Lucy and Jeremy's first date does not go as expected as they both keep on running into Lucy's ex-boyfriends. Although all's well that ends well by the end of the episode for everyone.

The striking resemblance of Robbie's new friend, Marie, to Mary raises eyebrows among discerning Camdens. Annie's invitation for her to stay for dinner makes things weirder for them. Back in Buffalo, unbeknownst to Robbie, Mary accidently bumps into her old boyfriend Wilson (guest-star Andrew Keegan) and his son Billy at the train station and makes plans to meet him for the evening. Mary is unsure on whether she should tell Robbie, but confides in her family about this. They all say that she should tell Robbie about this, but decides to ignore their advice. Also, Matt meets Robbie's ex-girlfriend, Cheryl, at the restaurant where she works. He starts to have feelings for Cheryl and tries his best to try to get her to go on a date with him. His efforts work by the end, but is having a hard time telling Robbie about his interest in his ex-girlfriend.

Mary returns home back to Glenoak for the summer to spend some time with her family, but fears about being together again with Robbie. Eric and Annie are recipients of what may or may not be advances from unmarried acquaintances. Simon and Deena see that they still have feelings for each other, even though she has a boyfriend. Matt agonizes over telling his family about his new relationship with Cheryl, but soon decides to tell them all. Lastly, Lucy surprises herself and others when making a proposal to Jeremy and the possibility of going to college in New York with Jeremy. Although plans change when Mary, feeling rejected by Robbie, makes a shocking declaration.

Mary tries to right a wrong by explaining to Lucy that she never had adult relations with her sister's fiance. The only problem left is trying to convince Lucy. Wilson unexpectedly drops by the Camden home from New York to see if he and Mary are really over by finding out her answer. James talks to Eric about him attempting to have an affair with Annie as Serena comes clean with Annie about her trying to have an affair with Eric. Robbie and Wilson set aside their differences so that they can talk about Mary. Matt learns a few things when it comes to Cheryl's honesty when she doesn't tell her friends that she's dating him.

Annie's father Charles shows up at the Camden household for a weekend visit as Ginger supposedly needs to get away for a bit. But Eric forgot to tell his wife about it and nearly everyone in the Camden household is too busy to spend time with the elderly man. So Grandpa Charles takes Simon to get his learner's permit for driving and they end up being the center of a televised police-pursuit. Eric lies to Annie about his plans for the day, which include a trip to Glenoak Hospital.

St. Valentine's Day delivers a few surprises for the Camden family. A grounded Simon is asked out by a senior. Annie's attempt to surprise Eric with romantic Valentine's plans backfires and results in a big fight. Mary discovers Robbie's plans with Joy. Lucy and Mary learn that Jeremy and Wilson both have dates for Valentine's. Matt seeks his fathers help as he wants to settle down, which leads him to seek out old girlfriends as to why they're no longer together. Ruthie is hesitant to go to a party because her friend tricked her into asking out a boy she's already going out with.