Annie and Eric get invited to go camping with Morgan and Patricia Hamilton. The kids are left home alone to care for each other. The older kids begin complaining about having their own plans, but they were forced into staying home and being responsible. Annie eventually lets the kids go to school and she will figure things out later about what will happen with the children.
At school, Matt and John discuss what will happen when their parents are gone for the night. They ask Keisha to babysit so that they can go out, but she says no and Matt is supposed to ask Mary to babysit. Ruthie wants to keep all of Happy's puppies and doesn't understand why you get rid of puppies, but don't get rid of kids. Mary tells Matt that she has friends coming over so she can't watch the younger kids. They plan that Matt and John will have their dates in the den and Mary and Keisha will have their friends in the living room. Lucy complains that she can't go on the date that she planned on with Jimmy, but Lucy agrees to bring the kids to the movies with her, but only if she is paid $10. Simon gets the puppies ready to go to their new home. Lucy tells Jimmy that she has to bring the younger kids with them to the movie, but Jimmy is not happy with doing something that is not approved by Lucy's father. Lucy negotiates the movie choice with Jimmy since he wants to go see a foreign film, so they agree to let the younger kids see a kids' movie while they see the foreign film that will be more romantic. Morgan and Patricia show up with all of the kids to pick up Eric and Annie to go camping. Lucy proposes going to the movies to the younger kids, but they don't really want to go and want to stay home. The people show up to take the puppies. The mother wanted to name the puppies Little Precious and Sugarplum, but the son wants to name the dogs Simon and Ruthie. Simon is sad when they leave with the puppies and doesn't want to go to the movies, but stay and watch Happy, but matt says that he will watch Happy for Simon. At the movies, the younger kids go to the cartoon movie, but they ask for money for the snacks, which takes all of Lucy's money.
At home, Matt and John both show up with their dates, but are interrupted by Mary and Keisha's friends in the living room. When they check on the girls, they find a party. They decide to join in the party. While camping, Eric and Morgan complain about it being cold and bugs. Annie and Patricia show off their lingerie to each other in anticipation for the night. Morgan gets a page from Patricia's ex-husband who calls every Valentine's Day. Morgan gets upset by the situation. At the movies, Lucy and Jimmy exchange Valentine's Day cards, but Jimmy's card is funny, not romantic like Lucy's is, so she gets upset.
At the Camden's house, there is a large party going on. Matt confronts some guys that are drinking beer, John gripes at Keisha for talking to a guy that is too old, and Mary finds a guy to talk to. Matt and John's dates find new guys to talk when Matt and John are busy policing the party. Eric is concerned about the kids and that they may be having a party, so he decides to call a policeman, Sergeant Michaels, to drive by the house. Simon and Nigel get in trouble in the movie theater for throwing popcorn and Lucy and Jimmy get caught kissing and they are told to bring the younger kids home since they are being kicked out of the theater. Sergeant Michaels shows up and breaks up the party. After getting everyone out the house, he tells Matt and Lucy that Happy has been run over by a car and that he will go with them to get her to the vet.
While trying to go to sleep, Morgan and Patricia decide to talk about Patricia's ex-husband's phone call. Morgan is surprised to learn that she was first married to a white, Irish man. Eric and Annie talk about how they didn't know that Patricia was married before. Eric gets a phone call that Happy got hit by a car, so they decide to leave right away. Matt finds out that Happy is ok and Sergeant Michaels brings him home so that he can tell Simon. Patricia feels responsible for suggesting the trip in the first place. The girls get the house cleaned before their parents get home. John brought the younger kids home from the movies. Jimmy apologizes for the funny Valentine's Day card. Jimmy tells Lucy that he wants to kiss her, but not on an artificial holiday like Valentine's Day. Matt tells Simon that Happy got run over, but that she is at the vet's office. Simon begins to freak out and cries to go see his dog. Matt tells him that he will bring him there.
Simon is at the vet's office crying over Happy. The vet tells Matt that Happy is not doing well. At the Camden's house, the older kids are still cleaning. The parents show up and the Hamilton's decide to bring their kids home. Each parent decide to divide the kids up and interrogate them about what happened. Each child tells the whole story and apologize about everything. After the interrogation, they don't think that they got the whole story, but agree that maybe it is for the best that they don't know everything. The Hamilton's leave, but not before Morgan and Patricia decide to put her ex-husband behind them. Matt called from the vet's and says that Happy is not doing well. Everyone decides to go visit Happy at the vet's. Eric declares that the kids will not have another party or go to another party as punishment for the evening's activities. The vet tells the family that Happy is unconscious and when she does wake up, Happy may still not be well. Simon fell asleep on the examination table next to Happy.
The whole family spends the night at the vet's office and Simon wakes everyone up by yelling that Happy is ok. Everyone apologizes to Happy about the night before. Simon wishes Happy a Happy Valentine's Day and tells her that he loves her.