Phoebe is at P3 with Piper. Prue's date, Sean, waits forlornly at the bar. Ever since the sisters' latest trip to the past, Prue has been obsessed about finding out who the Triad sent after them. Piper complains that she can't get close to Leo because she feels that "they" are watching; they've tried to have sex two nights in a row, only to have him abruptly orb out. Phoebe has her own guy troubles; she's getting impatient with how it seems Cole is only flirting with her. Piper calls Prue, who is on the other side of town. Prue wants to tell them what she found out about the village in colonial Virginia where Melinda Warren was born, but Piper is more interested in whether she'll make it to P3 with Sean. Prue, however, wants to do some more digging at home, and tells Piper to tell Sean that she's hung up at work. Piper sends Sean on his way.
Prue goes to the manor and finds the front door open and every mirror broken. An unseen figure jumps on her and knocks Prue over the couch. Prue flings it through a window. After the others arrive, Darryl checks the house and finds nothing missing. He dusts some fingerprints and asks the sisters for lists of any enemies they might have. Prue is way ahead of him, but the list she gives Darryl has a bunch of demons the sisters previously faced. Prue heads up to the attic, and finds the door unlocked. Darryl is worried that the sisters are too cavalier about their security, but Prue points out that they have their powers to protect them. Piper and Phoebe don't want to rule out a human culprit, but Prue instead calls for Leo and asks him to find out all he can about the Triad. She's convinced it's the same demon who tried to take the Book of Shadows two weeks earlier. Piper and Leo exchange playful glances.
The Triad summons Cole and tells him of their impatience. They have sent another demon, Troxa, after the Charmed Ones as "assistance", rather than to replace Cole. Back at the manor, Troxa turns invisible on the porch and peeks in on Piper and Leo making out. They talk about Piper's fear that they are being watched at all times and Leo agrees to give the intimacy a break while he gets information for Prue. Just as Piper and Leo kiss goodbye, Leo orbs out to check on the Triad, much to Piper's frustration. Troxa finds Prue asleep in the attic, with a chart she's made of possible culprits. Troxa tries to smother her with a pillow, but Prue wakes up and swats him across the room. Cole checks up on the sisters and offers to have a patrol car watch the house. Prue tells them about the latest attack; she's now certain it was a demon. Outside the front door, Troxa runs into Cole and starts to choke him, accusing him of saving the sisters rather than killing them. Troxa plans to strike again tomorrow night and does not want Cole there.
Prue notices her favorite shirt and Grams' necklace missing. Leo orbs in and reports that "they" know little about the Triad, except that they are at the highest level on the hierarchy of evil. Prue gives Piper and Phoebe pairs of sneakers so they'll be better prepared in case of another demon attack. Darryl reports that the fingerprints have no match in the FBI database. On hearing about the necklace and the shirt, Darryl suspects a stalker and thinks Sean is the prime suspect. Prue is skeptical, but Darryl points out little things like being stood up can set a stalker off.
Troxa goes invisible and sneaks into Cole's office. He picks up a letter opener and is about to stab Cole, but Cole picks up a fire extinguisher and sprays Troxa with it. Cole's done some research; cold makes him visible and he won't even know he's visible since demons can't feel. Troxa vows to come after Cole next after he kills the sisters.
Prue does a photo session with a wildlife expert clearly based on Steve Irwin. Unseen to her, someone is taking pictures of Prue.
Phoebe enters a back room at P3, looking for Piper, and finds her making out with Leo. This does not help Piper's anxiety about being watched. Back at the bar, the two sisters meet Prue; she has set a demon trap with the Book as bait and is carrying a crystal that will glow when the trap is sprung. Sean comes to P3 and Prue leaves to spend time with him. Meanwhile, Cole enters the manor and, finding nobody home, opens all the windows and turns on the air conditioner. He shimmers to the attic and tries to steal the Book of Shadows. The trap springs, he briefly turns into Belthazor and Prue's crystal glows. The sisters hurry away, leaving Sean slack-jawed.
The sisters, wearing the sneakers Prue gave them, enter the attic and find Cole in the trap. Prue suspects that Cole is a demon. Cole claims that he thought the house was broken into and leaves angrily. Phoebe finds a box of flowers on the porch and brings them inside. She's very angry at Prue, but Prue remembers that Cole has lately had a habit of being around for magical emergencies. Phoebe scoffs at the notion and thinks Prue has lost it. Piper notices the package. Prue opens it and finds the flowers all dead and worm-infested. Convinced that Sean is the stalker, Phoebe heads off to call Darryl. Prue finds it hard to believe Sean is so unhinged to stalk her, but Piper thinks Prue is getting tunnel vision.
Cole meets Troxa outside and tells him that he is welcome to go after the sisters. As Troxa goes invisible, Cole tells him the key is getting the Book.
Leo orbs in just as Piper and Phoebe are closing the windows, holding a giant Hershey's Kiss for Piper. Troxa enters the manor as the sisters and Leo close the windows. In the attic, Prue notices Troxa's reflection in a broken mirror and flings him into the wall. The impact turns Troxa visible, and he leaps at Prue, but Prue shoves him into the trap. Piper, Phoebe and Leo rush in just as Prue is making Troxa talk. He reveals the Triad sent Belthazor after them as well, then suddenly goes up in flames. Phoebe apologizes for doubting Prue earlier. The sisters and Leo find Troxa in the Book, and notice that cold cancels out his invisibility. Prue realizes that if someone hadn't turned on the air conditioning and opened the windows, she might have never seen Troxa. Leo tells the sisters that from what he knows about Belthazor, they'll need all the help they can get. The sisters find Belthazor in the Book, and Phoebe recognizes him as the demon who tried to take the Book two weeks earlier. Leo orbs out to alert "them." Phoebe notices Cole's name written on Prue's chart, and makes Prue promise to call Cole and apologize tomorrow morning.
Prue is developing pictures in her dark room and notices several pictures of her among them. While Prue wonders where those pictures could have come from, an unseen attacker shoves her face in one of the chemicals and drags her off. The next morning, Phoebe muses that the stalker is still out there even though Troxa is gone; much of what happened the night before doesn't fit a demon's usual MO. She calls Prue's cell phone. The stalker proves to be Abbey, a bartender from P3; she has tied Prue up in the manor basement. Abbey answers the phone and pretends to be Prue on the road. She has become obsessed with Prue, and wants to become her. She even puts on Prue's missing shirt and a dark-brown wig. Abbey pulls a gun, and wonders how she got flung through the window the other night. Prue flings Abbey across the basement with a squint of her eyes. Abbey lands against a shelf, which falls on top of her. Prue then pins her to the ground with a table. Still partly blinded, she flings glass at Abbey's face and stumbles up the stairs.
Darryl calls Piper at P3 and says he has a match for the fingerprints: Abbey. Piper and Phoebe open Abbey's locker at P3 and find pictures of Prue, Prue's favorite perfume and notes on Prue's movements. Phoebe touches one of the pictures and gets a premonition of Abbey shooting Prue. The two depart for the manor.
Prue, hiding in a closet, astral-projects behind Abbey. Spooked, Abbey shoots five times at astral-Prue, but astral-Prue reappears on the other side of the room. Abbey shoots another four times. While Abbey is distracted, Prue charges out of the closet and tackles Abbey. Prue tries to escape, but Abbey shoves her into the wall. Prue, still partly blinded, stumbles to the kitchen. Abbey follows her, reloads and fires. Suddenly, the bullet freezes in midair; Piper and Phoebe have come to the rescue. Prue flings a still frozen Abbey into a cupboard.
Marvelous 3 plays at P3 that night. Leo is installing an alarm system. Cole arrives, and Prue admits she still doesn't entirely trust him. Prue finally gets an evening with Sean, while Phoebe and Cole kiss for the first time. Leo and Piper go to bed after finally having sex, and she yells to "them," "I hope you enjoyed the show!"