The demon Xavier is trying to get to the Eternal Spring, which will heal his brother, Tull, and make the two of them immortal and invulnerable. To do that, he needs the help of the three nymphs who tend the spring. He kills their satyr and tries to force them to open the way to the Spring. The nymphs flee to San Francisco and The Charmed Ones.
Paige is busy being hyper-efficient witch-woman. She's rearranged the spices, indexed the Book of Shadows, and generally taken over all things witchy in Halliwell Manor. This also means that she has absolutely no life outside her role as witch.
Now that Leo's on paternity leave, Piper has time to be sister-in-charge again. She isn't terribly thrilled about Paige being in the leadership role. She's trying to reestablish dominance, and she's not all that subtle about it.
Phoebe isn't jockeying for position among the sister hierarchy - because she's too busy assuming the position with her hunky boss. After spending the night with him, she's worried that their relationship will put her job in jeopardy.
The nymphs are in the news, as they're shimmying around every guy with a wind instrument in the city. Phoebe's boss wants to get the story on these "Godiva girls." Piper and Paige stake out the fountain the nymphs are frequenting. When the nymphs show up, so does Xavier. He toasts one of the nymphs. Piper tries to vanquish him, but succeeds only in blowing up his hand.
Back at the manor, Piper and Paige fight over how best to deal with the demon. Piper banishes Paige from the attic while she tries to figure out what to do. The nymphs are doing their own plotting - they recognize Paige's repressed wild streak and decide to make her their new sister. At the same time, Phoebe's boss shows up at the door, wanting to talk. He witnesses the Godiva Girls, now with Paige, frolic off into the night in search of their new satyr. Phoebe won't tell him what's going on, which annoys him.
After a brief stop at P3, the nymphs hear their new satyr's call. But it's not a real satyr - it's Tull, Xavier's brother. Meanwhile, Piper and Phoebe track Xavier back to where he's hiding. They try to get him to tell them where Paige is , but he doesn't play nice. They vanquish him. By this time, Tull has conned the nymphs into opening up the way to the Eternal Spring. He drinks from the spring and gets the power. Paige, even in nymph form, figures out something is wrong. She morphs back into witch form and tries to stop him. She gets pummeled for her trouble. Tull shimmers back to where his brother is hiding, but finds the witches waiting for him. They try to vanquish him, but it's too late - he's invulnerable. They run away and call for the nymphs, who lead them to an injured Paige. A drop from the Eternal Spring heals her wounds. Tull comes after them. Since they can't vanquish him, Paige and Piper come up with a quick spell to turn him into a tree. Now he can't do any more damage.
Piper and Paige admit that they've both got skills, and agree to split head-witch duty. This gives Piper more time with Wyatt and Paige more time to have fun. Phoebe finally talks to her boss, who ran the Godiva Girls story but didn't make any mention of Paige. Phoebe shows her appreciation as only she can.