The demon Vicus is working on turning Wyatt evil.
Piper is worried about Wyatt - he's in regular nursery school, and he's spending the whole time talking to thin air.
Phoebe is heavy into her new psychology coursework, so she's prone to spouting psychobabble. Maybe Wyatt has an imaginary friend? She resolves to quiz one of her professors. That professor refuses to answer her questions, since she thinks Phoebe is just pumping her for pop-psych answers for her column.
Paige is frazzled - not only is she dealing with her Whitelighter charges, she's also dealing with a series of magical attacks every time the phone rings.
Piper and Paige determine that the demons attack whenever Wyatt's nursery school calls. As the demons seem to be attacking with powers that are supposed to belong to good witches, Paige theorizes that Wyatt himself is causing the demons to appear. Leo goes to pick him up. What he can't see is that Wyatt isn't talking to thin air – he's talking to Vicus, who is invisible to everyone but Wyatt. He's trying to win Wyatt's trust -- and his teddy bear. Vicus is pissed when Leo takes Wyatt away. He tells his followers, all good kids he had corrupted to the dark side, to keep the sisters occupied. Piper is tired of trying to figure out what's going on in her toddler's head, so she casts a spell to communicate with him. It goes awry – 25-year-old FutureWyatt appears. Unlike the goatee'd, black-clad Wyatt who haunted FutureChris, this Wyatt is perky, polite and clean-shaven. He's thrilled to see his family. When he goes up to see toddler Wyatt, he catches sight of Vicus. Vicus decides to redouble his efforts to corrupt toddler Wyatt, so he can use FutureWyatt to cause trouble in the hear-and-now. He gets the good-kids-gone-bad to attack the sisters in force, then persuades toddler Wyatt to give up his teddy bear when the sisters are distracted. He puts a curse on the bear that gradually turns Wyatt more and more evil. When he does, clean-cut FutureWyatt morphs into the bad boy we remember. He leaves with Vicus.
Evil FutureWyatt is disgusted to see his evil brethren hiding out below ground – they should be taking over! Vicus counsels him to be cautious. The sisters confer in the attic. Piper and Leo decide to go to magic School to see if they can reverse the curse, while Phoebe and Paige resolve to go after Vicus. Maybe if they kill him, the curse on FutureWyatt will be lifted? FutureWyatt and Vicus decide to lure the sisters to the lair so they can make sure the Charmed Ones don't reverse the curse. When Paige and Phoebe come down to the lair, Vicus hides himself. They start pitching potions randomly, until FutureWyatt reveals Vicus himself. The sisters vanquish him, but Wyatt stays bad – and glad of it. He sets the evil minions on the sisters, then goes after his toddler self and the book of shadows. He can't touch the book – he is evil, after all, but he does manage to snatch his toddler self.
The sisters know FutureWyatt needs the Book of Shadows to reverse the spell that brought him into his past. He won't attack when the sisters are guarding it, so Leo convinces them to give him a shot, even though he has no magical powers. He doesn't need them – he just needs to win the trust of his toddler son. FutureWyatt threatens to kill Leo, but Leo doesn't buy it – deep down, Leo knows even evil FutureWyatt still loves his dad. Leo convinces toddler Wyatt to give up the bear, and the curse is lifted. Evil FutureWyatt turns back to his good self.
FutureWyatt has news for all the sisters: Paige becomes an accomplished Whitelighter who teaches FutureWyatt everything he knows. Phoebe, he implies, will have a baby. And Piper – well, she needs to worry less. Piper tells him that will never happen.