Thanks to the money brought in at work by one of Clark Griswold’s inventions, a long life food preservative, Clark has enough money to take his wife Ellen, his son Rusty, and his daughter Audrey on a trip to Las Vegas — the land of sand, slot machines, and the Hoover Dam. In Las Vegas, Clark crosses paths with Eddie, the sloppy husband of Ellen’s cousin Catherine. Eddie and his family now live in the desert north of Las Vegas on what used to be an H-bomb test site. During the vacation in Las Vegas, Ellen becomes addicted to Wayne Newton, Rusty gets a fake ID and becomes a winning high roller, Audrey starts hanging out with Eddie’s stripper daughter Vickie, and Clark becomes addicted to gambling and starts gambling away the family’s bank account, which amounts to $22,600. Ellen’s obsession with Wayne Newton is making Clark jealous, and Clark keeps losing money at the casino. After losing so much money, can Clark find a way to get the money back and save the family’s vacation?