Paige enters the kitchen with Richard early one morning to find Piper trying to fix the garbage disposal.
"What's wrong with the disposal?" Paige asks.
"Not disposing," Piper says. "Washer not washing, cable not…cabling."
"Don't forget the sink upstairs."
"It's next on my list," Piper says. Now that Leo isn't around to take care of the odd jobs around the house, she's assumed responsibility for them.
Phoebe enters just as Richard finishes magically repairing the disposal. She takes Piper aside. "Didn't Richard lose it the last time he used magic? I mean, like, really lose it?" Though Piper shares Phoebe's concern, she's more concerned about staying out of Paige's private business.
Piper goes upstairs to unclog the sink. Suddenly, the outline of a woman's face bubbles out of the water. "Help me," the face says.
Piper takes her sisters to search for the "water lady" in a park near a pond. The water begins to bubble, and the Lady of the Lake rises out of the pond holding a sword. Demons descend on her. The sword flies into the air. The Charmed Ones fight off the demons, but not before they kill the Lady of the Lake. The sisters find the sword, Excalibur, sticking out of a rock.
Paige orbs the sword in the stone back to the manor. While Phoebe goes to work and Paige goes to her temp job, Piper babysits Excalibur. Magical creatures come to the manor to try to pull the sword out of the stone.
Paige discovers that her temp job is working as Phoebe's assistant. Though Phoebe is desperate for help, she's uncomfortable with the situation.
"I can't tell you what to do," Phoebe says. "I mean, how weird is that?"
"Well, it's no weirder than usual," Paige replies.
"Oh, I see."
"Just kidding. Sort of."
Paige manages to get Phoebe's work situation organized, but tension rises between them when the subject of Richard comes up. Their discussion is interrupted when Leo comes to orb them back to the manor to help Piper keep the creatures under control.
Frustrated with having so many creatures underfoot, Piper takes hold of the sword to try moving it elsewhere. Instead, Excalibur slides easily from the rock. The creatures bow to her, and a man named Mordaunt magically appears.
Mordaunt says that he's a teacher, there to instruct Piper on how to wield Excaliber before the Dark Knight attacks, trying to steal the sword from her. Mordaunt gives Paige and Phoebe the recipe for a potion that he says will vanquish the Dark Knight. Since they don't have most of the ingredients that the potion calls for, they go to Richard's house to make it. Phoebe is concerned that Richard has creature parts like fairy wings and gremlin ears among the more traditional herbs, insects, and fungi. Paige tells Phoebe to mind her own business.
As Mordaunt trains Piper, the lure of the sword begins to take her over. She and Excalibur are becoming one. She becomes oblivious to everything around her, including Wyatt.
Phoebe and Paige are adding ingredients to the potion when Richard suddenly stops them, explaining that the combination would cause an explosion.
"Why would Mordaunt do this?" Paige asks.
"Because he wants you dead," Richard says.
Phoebe and Paige go back to the manor. They try to explain to Piper that that Mordaunt is evil, but under the influence of the sword, she doesn't listen to them. She goes off with Mordaunt to establish a new Camelot. Leo explains to Phoebe and Paige that Piper isn't the new King Arthur, but the new Lady of the Lake. She's not meant to wield the sword, but to pass it on.
Piper and Mordaunt select their Knights of the Round Table, but Mordaunt kills them and absorbs their powers. This makes him strong enough to get Excalibur away from Piper. He goes to kill the true recipient of Excalibur: Wyatt. But Phoebe and Paige are ready for him. Wyatt orbs the sword away from Mordaunt, then sends it flying across the room, vanquishing Mordaunt.
That evening, Phoebe apologizes to Paige for interfering in her business. Grateful to Richard for saving their lives, she realizes that he's not evil. Meanwhile, Leo finds Piper playing with Wyatt. "How are we doing?" Leo asks.
"His highness seems content," Piper says.
"What about you?"
"I'm doing all right. At least I have my priorities straight now. I was so busy doing stuff and all I really wanted to do was hang out with him."
"Well, you should have more time for that now," Leo says. "I fixed the washer…and the sink, and the cable, and the toilet."
"Wow, I forgot how handy you were to have around the house."
"Pretty strange, huh?" Leo says.
"Kind of scary, actually," Piper says, looking at Wyatt. "We've seen what he can do without the sword. I can't begin to imagine what he could do with it."
"Well, whatever it is, it's meant to be," Leo says.
"It doesn't make it any less scary, though. But that's tomorrow's problem."