Eric and Annie put on their counseling hats when a very pregnant Julie appears on their doorstep prepared to leave her new husband Hank. Eric decides to take Hank out to dinner to discuss their issues. While they are at dinner, a very pregnant Julie goes into early labor. Unable to transport her to the hospital because Simon and Mary are out to dinner and Lucy is on a date, Annie does her best to calm Julie down. Hank and Eric return to the house just in time for the birth. Julie delivers a baby girl. Grateful for Eric's effort, Julie names the baby after him: Erica. Meanwhile, Lucy is disappointed when her date expects her to be 'the man', and Simon attracts the attention of an older female admirer.

Eric and Annie must deal with the emotional fallout as they learn about their kids tumultuous love lives. Mary upsets her parents by announcing that not only has she decided to skip college in the fall, but she is getting back together with Robbie. Matt is forced to choose between his girlfriend Shana (who has moved back to Glenoak for the summer) or his ex-flame Heather, who confesses that she still loves him. Lucy dates Robbie's cute brother Ronald, disappointing Andrew Nayloss who still harbors feelings for her. Also, Simon gets dumped by Deena and Ruthie takes advantage of her new boyfriend.

In the fourth season finale, Simon finds out the real reason why Deena wants to break up with him. Also Ruthie does her best to get back together with her old boyfriend Burt, while Lucy also tries to go after an old flame: Andrew Nayloss. Mary decides to take things slow with her relationship with Robbie and her life. Matt and Shana break up their relationship, but reconciles with Heather. At the end of the show, it shows Matt and Heather may have gotten married- but didn't.

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.