Matt returns home for a visit, as does Simon, and Annie and Eric worry that Simon may be having sex with his new girlfriend Georgia. Expectant mother Lucy refuses to shop for maternity clothing, prompting Kevin's fears that she hasn't quite grasped the reality of it all yet. Meanwhile, the first day of high school and kindergarten proves disastrous for both Ruthie and the twins.
Simon has trouble dealing with Eric and Annie about his sexual relationship with Georgia, further widening the gap when he reveals that he is on academic probation.
Eric tells Lucy that she will soon be the new associate pastor at the church, which relieves her about the dreaded abstinence lessons she will soon be offering. Simon goes to see a therapist and reveals that his relationship with Georgia has been a front for his feelings of guilt over his fatal car accident. Meanwhile, Martin has his suspicions when Ruthie gets a crush on a boy she met in detention.
Eric is approached by a single expectant mother about giving her baby away to a foster home, but during labor, decides she wants the baby after all, prompting Eric to try and find the baby's father.
As the presidential election heats up, Ruthie decides to learn all she can about global politics after being impressed with Martin's expertise on the subject. Eric and Annie begin to suspect each other of sitting out the last election, and Eric tries to teach Sam and David the importance of politics. Meanwhile, Kevin admits to Lucy, who is already nervous about registering, that he can't vote because he still is listed under his old address.
Eric solicits help from Mary's ex-boyfriend Wilson when a young new father named Charlie comes to him and tells him he doesn't feel ready for fatherhood.
During a night out, Kevin tries to help Martin with a lady named Venus by telling her that Martin's a rookie on the force. When she becomes interested, Martin is left panicking over the reality of his lie, which leads to Kevin being coaxed by Eric and Annie to straighten things out.
After Kevin discovers that Simon's been booted from his college dorm for housing a female guest, Eric intervenes, only to learn that the girl in question is a struggling foster child with three siblings. Eric then decides to spread the word about becoming foster parents to his church congregation.
The family begins to worry about Annie's strange behavior with Thanksgiving only two weeks ahead. It turns out that she's simply fretting about the fact that most of the family has made holiday plans of their own, with Matt and Sarah unable to stay in town, Mary and Carlos offering Ruthie a chance to come with them to Puerto Rico, Simon stuck at school, and Martin and Mac heading out on a camping
Simon and his girlfriend, Georgia, try and figure out how to tell Eric and Annie that Georgia is pregnant. Meanwhile, Lucy faints in a grocery store and is rushed to the hospital by Matt, but his attempts to locate Kevin, who is working on a case, prove to be extremely difficult.
A grouchy Lucy is forced to stay in bed following her return home from the hospital, with the family, especially Kevin, doting on her constantly. Ruthie inadvertently discovers a troubling e-mail on Martin's computer, which might have something to do with the bad mood and poor school performance he's been sporting lately. Meanwhile, singer Wayne Newton shows up at the Camden home with a message for Martin from his father over in Iraq.
Despite being told to stay off her feet, Lucy asks Matt to take her shopping for baby gifts, but when the two get stuck in a mall elevator and Lucy goes into labor, Matt is forced to rely on his medical skills. Meanwhile, the Camdens prep the house for a surprise baby shower, during which time Kevin reveals to Ruthie that the gift he bought for Lucy is a house of their own.
Annie worries when Lucy decides to have a meet-the-baby gathering at the house, fearing that Lucy will be exposing the baby to the guests' strange germs, but Kevin is left with parental self-doubt when Lucy takes charge to prove that she is more than capable with the baby.
Ruthie gets the go-ahead from Annie and Eric for her first date. But, the family immediately runs the gamut between a mixture of euphoric and protective instincts, as Lucy and Annie prep Ruthie for the date, while Kevin gives her a candid "talk" about boys, and Martin and Mac plan their approach to tailing the date.
The Camden family breaks into song on the Glenoak streets with classic song performances over the course of Valentine's Day.
Simon asks Matt to prescribe some birth control pills for his new girlfriend, which prompts the spreading of a rumor around the house that she is pregnant. Kevin and Lucy have to decide whether or not to sell their house when the original owners come by and want to buy it back, while tension runs high over Kevin's possession of a firearm in the home. Meanwhile, the Camden siblings try to conceal some serious new information about Mary.
Simon learns that his girlfriend, Sandra, has an STD and begins to panic, despite his consistent practice of safe sex with her, while at the same time, Martin and Mac spot Ruthie's new boyfriend, Thomas, on a date with another girl. Meanwhile, Matt, Ruthie, Kevin, and Lucy worry about their decision to cover up Mary's self-imposed disappearance by telling them she is pregnant.
Ruthie and Annie clash over Ruthie's desire to go out with Vincent and skip Annie's specially-prepared meal, and things get more heated when Annie discovers that Ruthie manipulated Lucy in order to make her escape.
Ruthie finds Martin's girlfriend Zoe passed out in a school bathroom and discovers from Zoe that her family can't afford to buy food. Even though Ruthie promises to keep her secret, Zoe still ends up angry with her after Martin's decision to breakup with her due to her so-called arrogance mistakenly leads her to believe Ruthie betrayed her confidence.
Simon comes home to Glenoak to anxiously await the results of an STD test. Eric tries to counsel a woman whose two daughters have sickle cell anemia and whose long-gone father has returned to try and get them some treatment.
Matt has trouble breaking the shocking news to Eric and Annie about Mary's divorce and subsequent relinquishing of custody over her child to Carlos. Simon has a new girlfriend, but decides he must keep his reasons for not wanting to have sex with her a secret.
Simon and Rose make a surprise visit to Glenoak to share their happy news with their families. Eric hides news of Mary's divorce from Annie.