Homer is fattened for a Mayan human sacrifice to prevent the world's end.

Homer tricks the priest into a sack and escapes the temple.

The priest realizes they sacrificed the wrong person and the world will end in 2012.

Homer sets his watch to the 13th baktun, then finds a strange object.

Lisa's lobbying leads to a particle accelerator opening, which disappoints Professor Frink.

A mini black hole forms after Willie's mop is thrown into the accelerator.

The black hole ends up in the Simpson house, causing chaos and feeding.

The black hole grows larger as more items are thrown in, including the cat.

Homer starts a waste removal business with the black hole, then a baseball ruins it.

Creatures from another dimension thank the Simpsons for their garbage.

Homer sets up cameras to catch a ghost haunting the house.

The family prepares for the ghost, with Homer excited for a massacre.

A demon appears and reveals a deal with Marge from her past.

Marge recalls summoning a demon as a girl and making a deal.

Homer invents a time machine to go back to 1974 for a cheap comic book.

Homer in 1974 meets his younger self and Barney, causing chaos.

Future Homer ruins young Homer's chance with Marge.

Future Homer returns to a changed present where Marge married Artie Ziff.

Homer and his younger self team up to fix the timeline.

A group of Homers from history fights future Homer.

Marge realizes she married the wrong man and should have chosen love.

The timeline is resolved, and the episode ends with a subtitle.