Cartman visits the optometrist, a man who makes fun of Cartman's weight problem, by calling him "Piggy". The optometrist dilates Cartman's pupils and Cartman shows up at school with his eyes wide open. The boys discover that Chef has been replaced by a new character called Mr. Derf, who does his best to entertain them in line. After school the boys go to Chef's home where they find out that Chef had quit his job. Chef has quit his job because he met a woman whose changed his life and helped him to see the error of his ways. The boys decide they need to do something to save Chef. The optometrist prescribes stupid looking glasses for Cartman and then staples to his head to make sure he doesn't take them off. The boys (with a bespectacled Cartman) visit Chef at his new job at an accounting firm. The boys appeal to Chef, but he tells them this is just something they are going to have to learn to deal with. He promises to meet the boys after work to play some ball. The following morning after he didn't show up to play ball, the boys return to his house. Chef tells the boys that he and Veronica are planning to get married.
Mr. Garrison tells the children about The Facts of Life, the TV show, not the real ones. The boys ask Mr. Garrison advice about their problem with Chef. He tells them about the "succubus syndrome", a woman sent from hell to suck the life out of a man. The boys plan to tell the Chef about the succubus, but Cartman is diverted for another trip to the optometrist. At Chef's home, the boys meet Chef's parents. Chef's parents tell them about all the times they saw the Loch Ness monster, who is always asking them for about "tree fiddy" ($3.50). Cartman gets his laser eye surgery, which goes bad, so he must wear bandages over his eyes. Veronica, the succubus, comes to Cartman's home to help the boys understand why she is going to marry Chef. Before she leaves she reveals her true self to the boys and tells them there isn't anything they can do about it.
At the rehearsal dinner, Chef's father tells the story about the time the Loch Ness monster impersonated his son. The boys arrive to tell Chef the bad news, Veronica is a succubus. Chef tells the boys to accept the marriage, or get out his life. Stan isn't going to give up. The boys seek a way to destroy the succubus. They learn that if they sing the song of the succubus "There's Got to be a Morning After" backwards they can destroy her. They've got three hours to learn the song. At the church, the boys start to execute their plan, but the tape jams. In the process the succubus reveals itself and kills Kenny. They get the taped restarted and finish singing the song backwards, causing the succubus to disappear. In the aftermath, Chef wonders what he ever saw in her.
Back at school, things are back to normal; Chef is back in job and singing. At the optometrist Cartman brings in Kenny's head, hoping to get an eye transplant.
Kenny dies when he is attacked after the succubus reveals itself at the church.