It is Homer and Marge's eleventh wedding anniversary and Grampa does not arrive at the Simpsons house to babysit the children (having mistakenly gone to Ned Flanders' house). As a result, they decide take Bart, Lisa and Maggie to a fancy restaurant with them. However, Bart objects and takes them to a family restaurant shaped like an airplane, which spoils Homer and Marge's evening together. Later that evening, Homer and Marge attempt to have sex, but lack enthusiasm. The following day, it is discovered Homer left the freezer door open (he had found a piece of cake from their wedding that had been there for years), causing the refrigerator motor to burn out. Homer and Marge make their way to a hardware store to buy another motor, but the car gets stuck in the muddy driveway in the middle of farm country. Homer and Marge rush into the nearest barn to avoid a sudden storm. A farmer discovers the barn door is open and suspects trespassers. He enters the barn, nearly catching Homer and Marge, who are hiding in the hay loft, but leaves after failing to locate them. When the coast is clear, Homer and Marge have inspired sexual intercourse in the hay loft.
Homer and Marge think their marriage has been recharged and go for a romantic weekend at a Bed and Breakfast, but soon fall into their old patterns. However, a maid walks in on them and they conclude they are both aroused when they risk being caught during intimate moments, so they have sex behind window curtains in a room full of people. Their love life is recharged and one day they begin to have sex on the same miniature golf course windmill where Bart was conceived. This time they come too close to being caught having public sex, and while they manage to escape, they have to flee through Springfield in the nude. At one point, only lawn objects cover their genitals (Homer is turned on by the dangerous situation, but Marge rebuffs his attempts). A little later, they even use a promotional hot air balloon which Gil Gunderson has been living in, with Homer's buttocks being dragged across a Crystal Cathedral after he fell out but managed to hold on to a rope. In the end, the two are seen in a football stadium, and a naked photograph of Homer and Marge appears in the local newspaper (with censor strips covering them) and are embarrassed by their indecent exposure. The next day, Bart and Lisa see the picture and their parents begin to explain sex to them. Before they go into detail, however, they decide to go back to the miniature golf course.
In a subplot, Bart and Lisa stay at the Springfield Retirement Castle with Grampa, and they discover a metal detector in his closet. While Bart uses it to look for a pirate treasure, they uncover an alternate ending to Casablanca. The Old Jewish Man reveals that he was once a studio executive who tried to add the happy ending to the film. He pays Bart and Lisa to re-bury it, along with a "killing spree ending" for It's a Wonderful Life.