Dad and Mom are completely bored, so bored that the roast pig that Mom made runs off.
Timmy wishes for a sub sandwich, so Cosmo poofs up a sandwich with a submarine inside and eats it. Wanda warns him that it will give him a stomach ache. Later that night, Cosmo sleep walks with the sub periscope in his ear and a blanket over his body, so Mom and Dad think he is a ghost. After Wanda and Poof (also disguised as ghosts) take Cosmo away, Mom and Dad decide that they're no longer bored and that it's time for the Polter-Geeks. They then explain to Timmy that before he was born, they had a life as ghost hunters. Dad then shows him VHS tape from the 80s. It seems that they operated by blowing up a house they think is haunted, resulting in them destroy pretty much all of Dimmsdale. Chet Ubetcha then called an angry mob and expelled the from Dimmsdale, or at least chased them half way across town. They moved to the other side of the city and change their names; Dad use to be called Mom and Mom used to be called Barnaby. Convinced that there are ghosts in the house, they decide to blow it up. Timmy, however, tries to convince them to catch the ghosts instead. Timmy then asks his fairies to play along to keep the house from being destroyed. After Timmy wishes for a ghost cage, Dad and Mom go back in business. To prevent them from blowing up houses again, Timmy asks Wanda, Cosmo and Poof to haunt all the houses in Dimmsdale. In exchange for their services, they are paid quite handsomely. Upon reaching Mr. Crocker's house, instead of searching for ghosts, Timmy suggests blowing it up, which they do.
After a while, the fairies are fed up with being locked in a cage over and over, and as everyone in Dimmsdale think the Polter-geeks are heroes, they can stop, but Chet Ubetcha comes and says he will expose them as phonies again; and no amount of throwing money will make him go away. So Timmy wishes a spooky mansion up on a hill to make his parents official ghost-busters. Later that night, Mom and Dad are ready, but they have new equipment: some "ghost" catching devices Crocker gave them. But they don't catch ghosts, they catch fairies. So Timmy is covered by peanut butter and money (which ghosts love). Timmy tries to warn Cosmo, but it is to late, because Dad catches him. So he goes to warn Wanda, but Mom catches her before Timmy could warn her. Poof saw both his parents get caught by the Polter-geeks, and is deeply sad. So when Mom and Dad are about to throw Cosmo and Wanda to Crocker's "ghost" chipper, he changes his sadness for rage. He turns into a giant round Frankestein's monster and saves his parents. Chet Ubetcha admits ghosts are real and that Mom and Dad are successful. But when Poof throws the chipper to Mom and Dad, they end up in the hospital. Cosmo attempts to eat a knuckle sandwich, but he puts a fist between breads, the fist knocks him out, and the fishbowl gets stuck in his head. Mom and Dad mistake him for an alien and revive their other older job: alien hunting.
Cosmo then flies away from them as fast as he can.