After receiving an award for being Springfield's oldest citizen, Mr. Burns decides to take a trip with Mr. Smithers to the Mayo Clinic for a complete check-up. While he's away, he asks the Simpson family to look after his mansion. Right away, Homer, Marge, Bart and Lisa begin to act like snotty millionaires, sliding down the banister, riding a horse down the hallway, scratching their butts with the good silverware and so on. All goes well until Homer decides to throw a party aboard Mr. Burns' prized yacht, Gone Fission, and invites Moe, Barney, Lenny and Carl along. Meanwhile, at the Mayo Clinic, Mr. Burns goes through a series of painful and invasive tests that yield some pretty shocking results: It turns out that Mr. Burns has every disease known to man and a few new ones that haven't been discovered yet. Luckily, all of the diseases cancel each other out and Burns remains the picture of health, sort of. Back on the boat, Homer and his buddies are taken hostage by a group of pirates who throw them overboard. As luck would have it, the group survives and Homer returns to his family just as Burns returns home. Marge and Lisa have cleaned the house so there is no evidence of the Simpson family's messy stay and everything goes back to normal.