Robbie is ecstatic when his long-lost father (guest-star Alan Thicke) who is a dead-beat dad appears out of the blue. Although, Eric and Annie distrust the dead-beat dad's motives. He also convinces Robbie to move out with him; against Eric's wishes. Meanwhile, Ruthie turns to Mary for advice on how to get around their parents rules when wanting to buy a makeup kit that they said 'no' to. Also, a very convinced Annie worries when Lucy starts having a relationship with her friend's freewheeling ""unmotherlike"" mom. Also, Simon develops a bad attitude with his mother when not wanting to do his school work, but wants to hang out with his friends.

Annie discovers that the particularly flirtatious mother of one of Lucy's friends, Serena is seeing Eric for therapy sessions. Annie strongly requests that he refers her to someone else. Annie then has to deal with the guilt over her jealousy-induced interference between the two. Also, Simon is mortified when word gets around school over the fact that he's a virgin. Annie had shared the details of Simon's sexual inexperience with his ex-girlfriend's (Sasha) mother, Rita. Meanwhile, Matt struggles about telling Robbie he's interested with his ex-girlfriend, Cheryl. Lastly, Robbie is also hiding a secret from Matt that involves his ex-girlfriend Heather.

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.

Eric tries to arrange a romantic evening with Annie, but Annie keeps turning down every attempt he throws at her. At the same time, Annie takes Eric by surprise with the news that she would like to quit college and to start teaching to help get her out of her depression. Meanwhile, Simon is at risk of being fired from his new job at the pizza parlor by his excessive tardiness and discovering that waiting tables takes more people skills than he's equipped to handle. Also, Robbie sets Lucy on a date with one of his friends while Matt is concerned about a woman who keeps showing up at the clinic a lot. Lastly, Mary performs terribly in fire fighting training distracted by her consuming relationship with Wilson.