The Camden chaos continues with Matt, who is trying to salvage his marriage, questioning whether he still has feelings for his ex-girlfriend Heather; Simon's return to Glenoak creates conflicted feelings for his ex-girlfriend Cecilia, who is torn between her feelings for Simon and her current boyfriend Martin; Ruthie's foreign exchange student friend Maria, appears to be making the moves on Ruthie's boyfriend Peter; and grandparents-to-be Eric and Annie hop a plane for New York, despite Mary's repeated pleas for her family to stay away.

In a video essay for his application to college, Simon recounts the experiences of his family members including their relationships, friends and mistakes that they've made over the years in Glenoak as well as his own pain at having killed a young boy in a car accident earlier in the year.

Matt returns home to tell Eric and Annie that Sarah has left him and he's dropping out of medical school. Rabbi Glass offers Matt marital advice. Meanwhile, Kevin must decide whether or not to tell a very jealous Lucy that his ex-wife is in town and they got invited to dinner with her. Martin's aunt asks Eric to step in and talk Martin into moving to New York with her and Chandler asks Peter how he would feel about Chandler marrying his mother someday. Peter thinks something is amiss when his mother goes out of town for a business trip. Ruthie keeps something from her mother.

Matt returns to Glenoak to celebrate a special anniversary with Ruthie and tries desperately to avoid seeing the rest of the family. However, when Lucy discovers the secret, she, Eric and Annie go crazy trying to figure out why he's in town. Meanwhile, Martin shares something special with Cecilia. Also, Annie lets it slip to Nurse Kelly that Matt and Sarah are married. Lastly, Vic invites Paris to spend a special evening with him, but she doesn't want to go because she thinks he might propose.

During his Sunday sermon, Eric proposes that instead of a financial contribution, everyone should make a commitment to reach out and help someone in need. Kevin suggests that he and Lucy work together to set up a neighborhood watch program, but she feels passionate about working with Habitat for Humanity. Eric calls his new son-in-law Carlos (guest-star Carlos Ponce) and asks him to fly in without Mary for dinner with the family, which makes Carlos very nervous. Also, Ruthie picks a shy new girl at school as her project and soon finds out that she has a secret. Meanwhile, Peter picks Ruthie as his project, which prompts her to tell him that they should spend less time together. Chandler and Roxanne keep running into each other stirring up old feelings. Lastly, Annie becomes jealous of all of the time the twins are spending with Cecilia.

Matt and Sarah begin their student rotation in the ER, but get off to a bad start by arriving late and angering Dr. Norton, the attending ER physician. Matt and Sarah's relationship is tested when Matt quickly demonstrates an aptitude for the work, but Sarah accuses him of trying to make himself look better than the other students, especially her. However, Matt ends up looking foolish when he can't figure out how to turn off the ringer on his cell phone and he gets stuck fielding calls from his family. Matt's day ends tragically, leaving him to question his destiny.

It's Camden chaos all around when Matt, who is having problems in his marriage to Sarah, returns to Glenoak for a visit and runs into his ex-girlfriend Heather on his flight to Glenoak. Simon unexpectedly announces he's coming home for the summer. Also, Lucy sets out to discover why Roxanne is suddenly too busy to hang out with her as she's convinced that Roxanne is secretly trying to become a detective behind Kevin's back. Ruthie keeps a secret about a fellow student from her parents. Lastly, Martin learns that his baseball teammates think he's having sex with Cecilia.

With Annie out of town, Eric is left alone to accompany Simon on his visit to the Board of Education to discuss early graduation. During the meeting, Simon bonds with his advisor when they realize that they're both preachers' kids. Meanwhile, Lucy catches Chandler kissing a beautiful blonde woman at church and she agonizes over whether or not to tell Roxanne; Detective Michaels tricks Kevin into babysitting his six-year-old granddaughter; Peter makes a deal with the school bully in an attempt to protect Ruthie and Cecilia agrees to watch the twins which leads to a confrontation with Simon.

When a mysterious stranger wanders into the Camden home and spends the day with the family everyone assumes he is Simon's friend. Meanwhile, a disheveled, Rabbi Glass stops by to confide in Eric that he caught his wife kissing another man and discusses about splitting up. Kevin feels emasculated after being attacked and injured by a woman during a domestic disturbance call and goes on medical leave. His attitude toward Lucy changes drastically as he worries that Lucy isn't attracted to him anymore. Plus, Simon is concerned that no one seems to care that he's leaving for college in a couple of days. Lastly, Ruthie and Peter struggle with a school project.

Eric is brought in by the school board to help investigate the local high school Principal, when more than one concerned parent questions her behavior. When a female student disappears, all fingers point at Ms. Jones, but Eric believes strongly that the student's father may be the real culprit. Elsewhere, rumors about Martin upset Cecilia, who then regrets talking to Ruthie about her feelings.

Prospective homeowners Lucy and Kevin are ready for a fight to the finish when they learn that Chandler and his soon-to-be-adopted son Jeffrey are their rivals in a bidding war on a house. However, the conflict sparks an idea with Eric and Annie who decide to use their savings to buy their house from the church. Meanwhile, Ruthie is upset with Martin because she thinks he will get the garage apartment instead of her when Lucy and Kevin move out, and Peter suspects that his dad might be having an affair.

In the eighth season premiere, the Camden's spend the last week of summer at a beach house. At the beginning of the summer, Simon killed Paul Smith in an automobile accident. Simon is having a hard time dealing with the fact that he killed him and everyone tries to help him. Eric and Annie try to push Simon to go back to school which begins in a week. Eric would like Paul's parents (guest-stars Katie Mitchell and Mark Moses) to accept the insurance companies offer to the money. Paul's brother vandalizes the church by adding graffti to the sign saying "Thou Shalt Not Kill." Simon runs away to New York to get away from the troubles he is having in Glenoak. Also, Lucy and Kevin discuss possibly having a child. Peter is spending a lot of time around Ruthie and the Camden family. Ruthie finds out about Mary and Carlos being married.

Mary makes a surprise visit home to deliver unexpected news to Eric and Annie. Meanwhile, Simon tells Cecilia that he needs space. Also, Lucy and Kevin adjust to married life. Chandler breaks up with Roxanne after learning that she isn't comfortable with the idea of being a preacher's wife, while Roxanne seeks Kevin's advice on dealing with a dispirited Chandler. Also, the Camdens finally learn who's pregnant. Lastly, Eric ponders Simon's academic future and Annie prepares for a potentially tense dinner engagement.

Lucy finds her husband Kevin and his partner Roxanne in a compromising position while on an undercover police assignment, Cecilia and Martin's relationship hits another bump in the road when their after-school commitments get in the way of one-on-one time, and Chandler may have bitten off more than he can chew as a new parent. Ruthie and Peter get stranded after missing their bus during a school field trip. However, fate intervenes when the youngsters cross paths with Lost Boys Nicodemus and Jacob, who not only take care of them until Reverend Camden arrives, but also share the heartbreaking story of their struggle to stay alive.

A distraught Peter learns that his alcoholic and mean-spirited father who abandoned his family three years ago, has changed his ways and wants to be part of Peter's life again. In the wake of this monumental news, Chandler must decide how this will impact his relationship with Paris and Peter. Meanwhile, Ruthie feels that Peter is pushing her away during this chaotic time and Reverend Camden finds a philanthropic way for the community and his family to embrace Vic.

Eric feels he must intervene when Martin, who recently moved in with the Camdens, is recruited by a professional baseball team, the Miami Gators and considers dropping out of school. Meanwhile, Ruthie enlists Lucy's help to convince their mom that she should be allowed to attend a couples party with Peter. Finally, Chandler's mother pays him an unwelcome visit when he is named executor of his father's estate. A rift happens between Lucy and Annie where an angered Lucy considers moving. Lastly, Cecilia teaches Sam and David on how to ride a bike.

On a temporary leave from military duty in Iraq, Martin's father pays the Camdens a visit to help his son decide whether to forgo college for a career in professional baseball. However, the visit turns sour when Martin catches his father kissing Roxanne. Meanwhile, Chandler and Paris reevaluate their relationship in the wake of her ex-husband's return, and Roxanne comes to blows with Martin's aunt over their differing views on the war in Iraq. Lastly, Vic tries to join the Marines and talks to a supervisor over the matter.

Eric and Annie throw a "Welcome to the Neighborhood" party for Ruthie's Muslim friend Jill Dupree and her parents, but the Duprees are hesitant to attend. Eric is shocked and disappointed when he learns that his neighborhood is not a friendly place for Muslims. Meanwhile, Cecilia's house is robbed while she and her dad attend Kevin's first Neighborhood Watch meeting; Roxanne mentors a troubled sixteen-year-old and suspects that he might be involved in the robbery, and Chandler finds himself attracted to Peter's mom Paris.

Annie's half-sister Lilly is getting married and wants their ailing father to walk her down the aisle but Annie worries that the strain might be too much for him. Meanwhile, Fred and Mrs. Bink attend premarital counseling with Chandler, but Fred's mother tries to put a stop to the wedding because she thinks Mrs. Bink is a gold digger. Lastly, Jimmy and Pat, two mentally challenged people, decide to get married after just one date and ask Chandler to perform the ceremony, but Jimmy's parents try to put a stop to it.

Eric arranges for Peter and his dog to visit a drug rehab center to cheer up the patients. Peter bonds with Nick and helps him reconnect with his estranged son. Lucy finds out that Kevin has been secretly coaching the Glenoak Police Department husband-and-wife softball team and demands that she be allowed to play. Just before his first date with Paris, Chandler receives a letter from Roxanne telling him she still loves him. Martin confronts Cecilia about her lingering feelings for Simon, prompting Ceclia to call Simon to let him know she has a new boyfriend. She is also surprised when he admits that he is also dating someone and Ruthie is jealous of Cecilia and Annie's close relationship.

Annie's half-sister Lily shows up on her doorstep to discuss an important family matter after Annie refused to contact her. Eric tries to figure out why Annie won't contact Lily. Meanwhile, Cecilia sets Martin's friend Mac up with a girl from school, but he doesn't want to go out with her because of something embarrassing that happened ten years ago; Ruthie and Peter put a bad spin on a school project that lands them in trouble when they create a newspaper featuring false and derogatory stories about two former US presidents. Lastly, Roxanne turns to Chandler when she finds herself faced with a moral dilemma as she is keeping a secret from Kevin regarding Detective Michaels.

Lucy and Kevin celebrate their one-year wedding anniversary and contemplate whether they're ready to start a family, but things don't go off smoothly as Lucy refuses to drink champagne with Kevin during their anniversary dinner. Cecilia and Martin realize that their relationship may face a rocky future if Cecilia goes away to college. Chandler's foster son asks him to rid their house of all alcoholic beverages. Peter lies to Ruthie about his plans for the evening when she asks him to help her baby-sit the twins. With that, Peter goes missing, but concern turns to disappointment when Eric and Vic find him drinking alcohol with his friends at the park.

The Camdens, especially Lucy and Ruthie, grow concerned that an unusually joyful Annie isn't dealing with her true emotions following the death of her father Charles, but the happiness proves to be infectious as it soon spreads through the family and all over town. Meanwhile, Eric tries to convince an unhappy Chandler that he should consider adoption. At the same time Chandler is approached by a mysterious young girl who gives him a cryptic message before she disappears.