A demon attacks Paige, Piper and Chris in a parking garage. The three fight her off and she transforms into a spider as she flees. Chris is scratched, and worried both for himself and for his younger self in Piper's womb. Back at the manor, Paige finds the demon in the Book of Shadows.
The Spider demon, in her lair, meets an old man cocooned in silk. She has been feeding on him and he begs for mercy. He notes that she has returned empty-handed, but she says she has infected Chris. She finishes the man off.
A man in green meets Paige at P3, which is not open yet. He claims to be a leprechaun and to have been turned human by a wicked witch, and that he could no longer bestow luck. Paige says a quick spell and the leprechaun returns to his normal (diminutive) height. He says his name is Riley and gives Paige his shillelagh.
Chris is feeling ill and his eyes are dilated. As the sisters prepare to bless a vanquishing potion, the spider demon appears, wrapping Piper in a cocoon and sticking her to the wall. As Paige throws the potion, Chris turns on her and Phoebe. The demon turns into a spider and flees.
Paige calls for Leo, who recognizes the work of the spider demon and assures the sisters that Piper is safe for now. Chris is locked in the basement and Leo tries to talk to him, but Chris attacks with spider silk. Leo orbs away in time. Phoebe admits to Leo that Chris is his son, which is difficult for Leo to accept. Leo says the last victim of the spider demon was a wizard, and there might be something helpful at Magic School.
The spider demon calls telepathically to Chris and demands the cocoon. Chris tries to resist her call but is having a hard time.
Paige meets three more magical beings that have been turned human: a Nymph who has been turned into a balding man, a Fairy who has been turned into an old woman, and an Ogre who is a shortish man. We see the wicked witch, a cackling stereotype straight out of The Wizard of Oz, stirring a cauldron. She disappears in a flash of light as Paige casts a spell and the three beings return to normal form.
At Magic School, Sigmund tells Leo of Rathmere, a wizard who mysteriously disappeared in 1904. Gideon scolds Leo for abandoning the Elders. Leo tells Gideon he is trying to save his son. Not Wyatt, but Chris. Gideon is clearly surprised and, when Leo departs, reaffirms his determination to do away with Wyatt for "the greater good."
Chris turns into a spider and slips out of the basement. Phoebe channels his anger and vocalizes his feelings. After leaving spider form, Chris, with silk, binds the hands of Phoebe, Paige and Leo, and orbs away with Piper. Paige remembers the shillelagh and orbs it, calling Riley. Riley grants Paige some luck (unclear whether it is good or bad given that she crashes to the ground) and her hands slip free.
The spider demon begins to feed on Piper's magic, and Chris collapses in pain. The spider demon tells him that she's feeding on his magic, too, through Piper's baby.
Leo scries for Piper as Paige walks in with the nymph, the fairy and the ogre. The ogre pounds on the door to the spider demon's lair, annoying her. She comes out and the fairy flits in her face. The nymph throws a potion and she turns into a spider and tries to escape, but the ogre steps on her.
Leo frees Piper of her cocoon and orbs her away as Chris approaches. He seals the spider demon's door with silk and entangles Leo in a web. Leo fuels Chris' anger with mocking questions about why he hates him, and Chris snaps and begins to viciously beat his father, who makes no effort to fight back. Outside, Piper takes an antidote for the spider demon's venom, protecting both baby and adult Chris. Chris immediately reverts to normal, but continues to beat Leo until Piper enters and pulls him off.
Piper agrees to stay at Magic School with Wyatt, unaware of Gideon's plans for Wyatt, while Leo decides to remain in San Francisco with the Halliwells on the grounds that he belongs with his family.
Meanwhile, Chris is brooding atop the Golden Gate Bridge when Leo orbs in, begging to know what he did to make Chris hate him so much. Chris explains that, while Leo was there for Piper, Wyatt, and half of the world, he was never there for him. Leo suggests that Chris traveled back to save their relationship as well as Wyatt; with tears in his eyes, Chris simply says, "I doubt it," before orbing away.