Having become frustrated with too many electric bills, Homer places a windmill generator in the backyard. When he sees that the excess energy goes back to the power company, he takes the house off the power grid, making it entirely dependent on the windmill. Then a violent windstorm hits Springfield, and among the victims are the windmill and a whale which ends up beached, prompting Lisa, Homer, and the other townspeople in an attempt to save it.
Seeking a cheaper, alternate source of energy, the Simpsons put up a windmill generator in their backyard. But once Homer discovers that the windmill's surplus power is being sent back to the power grid (and therefore to the electric company), he refuses to be a part of anything that benefits "the man" and has their home removed from the power grid. This leaves the Simpsons completely dependent on the windmill, which proves to be an untrustworthy source of power: they only have electricity when the wind is blowing. The electricity comes and goes, thus having problems with the garage door, watching TV and playing the Zii. Bart climbs to the top of the windmill to spin it and prays to God to blow wind. Ironically, a huge windstorm blows into the Springfield area, giving the Simpsons electricity galore until the windmill is knocked out of commission. The next morning, Bart and Lisa walk around looking at the damage from the storm, and discover that a 150-foot-long blue whale has beached itself.
Lisa names the whale Bluella. Homer takes Lisa to help the whale, but Marge read that whales that spend too much time out of water die, so tells him not to give hope to Lisa. The entire town tries to help the whale get back into the ocean by pulling it off shore, but without success. Lisa comes to care deeply for the whale, reading poetry to it at night and falling asleep beside it. She dreams of the U.S. military coming to the whale's rescue, lifting it up with a net and dropping it back into the ocean. In her dream, Lisa is overjoyed to see the whale frolicking in the ocean. The whale then jumps into the stars and swims through the galaxy, which makes Lisa feel confused.
Lisa wakes up from her dream to observe that the whale has died, which makes her very crestfallen. Bart goes to the beach and sees the police preparing to blow up the whale. They place dynamite around the whale and detonate it, only to spread parts of the whale all around the beach. They use the whale to make food, perfumes and other whale products. But Lisa starts to hear whale squeals, which just come from normal sounds through the town (like Moe oiling his bar's door hinges and a mime inflating some balloons). Also seeing Martin getting a wedgie in the alley by Nelson making a loud noise. Later, Lisa is standing at the docks and sees the whale's two calves surrounded by a group of sharks. She feels helpless to do anything until Homer drives up to the dock in a boat he claims he is trying out. Lisa and Homer try to fend off the sharks, but are stopped by two activists in another boat labelled the "Sea Huggers." Homer ends up in the water with the sharks. The sharks turn their attention from the whale calves to Homer, thinking that Homer is another whale. Fortunately, the whales' father comes just in time and rescues its calves and Homer. The episode finishes with the family going back home to draw pictures of the father whale forming a romantic relationship with an octopus. The pictures are shown during the closing credits, while the song "la mer" ("the sea" in French) from Charles Trenet plays.
This episode was one of the best-received season 21 episodes due to its emotional storyline. IGN named this one of the two best episodes of that season, the other being "The Bob Next Door".