On a stormy night in San Francisco, a woman by the name of Serena Frederick situates herself in front of an altar, lighting a few candles using only her finger. She starts chanting and meditating, just as someone sneaks up behind her, startling her. Once she sees who it is, she recognizes them and relaxes, but then, they brandish a dagger, stabbing her with it. Meanwhile, another woman by the name of Piper Halliwell returns home in the rain, having been grocery shopping for a job interview at a restaurant. Her older sister Prue shows her a wooden spirit board she found in the basement, on the back of which is a cryptic message from their late mother, reading: "To my three beautiful girls. May this give you the light to find the shadows. The power of three will set you free." Prue suggests they send it to their aimless younger sister Phoebe in New York. Piper, however, defends Phoebe, insisting that Phoebe's getting her life together. Unimpressed, Prue walks off, and Piper follows. As soon as the room is empty, the pointer on the spirit board starts moving on its own.

Back at Serena's apartment building, Inspector Andy Trudeau correctly guesses that Serena was a witch, deducing that she was killed with an athame, a ceremonial dagger used by witches. His partner, Darryl Morris, however, is skeptical. Just then, they're approached by Jeremy Burns, a reporter who asks about Serena's murder, pointing out that she's the third victim in as many weeks. Meanwhile, back at the Halliwells', Piper gently breaks the news that Phoebe lost her job in New York and is moving back in with them, much to Prue's chagrin. Prue asks when Phoebe's due to arrive, just as the woman in question enters, having found the hide-a-key outside. She says she took a cab from the airport, and that she has no money to pay for the fare. So, Piper grabs Prue's purse and goes to pay, leaving her sisters alone together. Things are tense between them, as apparently, Prue's still mad at Phoebe for some incident involving Roger, Prue's "Armani-wearing, Chardonnay-slugging trust-funder" former fiancé, even though Phoebe insists she never touched him. Piper returns, offering to make dinner, but her sisters each insist that they're not hungry. Later, however, Piper brings Phoebe something to eat. She then notices Jeremy Burns on TV during a news report, and points him out as her boyfriend. Returning her attenion to Phoebe, the sisters get to talking about Prue, with Piper defending their big sister, pointing out that Prue sacrificed her childhood to raise them. Back in Serena's apartment, meanwhile, Andy finds a tattoo of a triquetra on Serena's neck, and remarks that the other two victims had the same tattoo. Just then, Serena's cat, Kit, jumps onto a nearby table, getting their attention, and that's when Andy notices the triquetra symbol on Kit's collar.

Back at the Halliwells', Piper and Phoebe are playing with the spirit board, as Piper is telling Phoebe that she and Jeremy met at the hospital six months ago, after the sisters' Grams was admitted. Piper then gets up and heads for the kitchen, just as the pointer on the spirit board starts moving on its own, freaking Phoebe out. She draws Piper's attention to it, but Prue appears and she and Piper accuse Phoebe of moving the pointer herself. Eventually, however, the pointer begins moving again, spelling out the word 'attic'. Just then, the storm knocks out the power. Prue and Piper head to the basement to check on the circuit box, while Phoebe heads for the attic. Initially, she finds the door locked, but then, it opens on its own and she begins exploring. In a trunk, she finds a thick tome with a triquetra on the cover, called The Book of Shadows. She begins flipping through it, finding an incantation and reading it aloud. Downstairs, a light shines down on the dining room chandelier, and a picture of the sisters magically changes so that they're standing closer together. Prue and Piper enter the attic, wondering what Phoebe's doing and how she got into the attic in the first place. She explains what just happened, and says that the three of them are about to receive powers. The sisters then head back downstairs, remarking that they don't feel any different, while someone stands outside in the rain, staring up at the house.

The next day, Piper finds Phoebe outside on the front steps, sipping coffee. Apparently, Phoebe stayed up all night reading The Book of Shadows, and learned that their ancestor, Melinda Warren, was a witch with the powers of telekinesis, premonitions, and the ability to stop time. Phoebe adds that Melinda was burned at the stake, but not before prophesizing that her bloodline would eventually culminate in three sisters who would not only be good witches but "the most powerful witches the world has ever known," known as the Charmed Ones. Phoebe believes she and her sisters are those witches. Meanwhile, at the Museum of Natural History, Prue is informed by Roger, her boss and former fiancé, that he's taking over an exhibit she curated. She walks off, furious, and a pen in Roger's shirt pocket starts leaking, staining the shirt. He takes it out, and it squirts him in the face with ink. At a restaurant called Quake, meanwhile, Piper is preparing an audition recipe, when the head chef, Chef Moore, enters and announces that Piper's time is up. She tries to explain that she didn't have enough time to add wine to the sauce, but he ignores her and goes to take a bite. Nervous, Piper begins waving her hands about, inadvertently freezing Chef Moore in place. Initially, she's confused, but then, takes advantage, using a baster to squeeze some wine onto the bite Chef Moore was about to take. When he unfreezes, he bites into it, expressing his approval. Meanwhile, back at the museum, Prue winds up quitting her job, citing it as the best thing she's ever done, aside from breaking up with Roger. He's a snot about it, though, so as Prue's leaving, she pantomimes strangling him, not realizing that the gesture causes his tie to magically tighten. Fortunately, he quickly manages to cut the tie off before he's strangled to death. Piper, meanwhile, is at a pay phone, trying to get ahold of Phoebe, when she runs into Jeremy, who congratulates her on getting the job. At the same time, Phoebe is riding her bike, when she receives a vision of two skaters, one of them getting run over by a car. As she continues on, the scene from her vision plays outs, except she's able to save the skaters from getting run over. However, she falls off her bike in the process, enough to warrant a trip to the hospital. Prue later arrives at the hospital, asking about Phoebe, when she runs into Andy, who's there to speak with the coroner. Apparently, she and Andy are old friends, but haven't seen each other in a while. That night, Prue takes Phoebe to Quake, where they discuss their powers and being the Charmed Ones. As they're talking, Prue accidentally discovers her telekinesis. Then, Phoebe informs Prue that there are two kinds of witches: good witches who fight evil and protect the innocent, and bad witches, or warlocks, who live only to kill good witches and steal their powers.

Piper and Jeremy, meanwhile, are on their way back to his place, when Jeremy suddenly decides to take Piper to an abandoned warehouse to show her the view. In the meantime, Prue and Phoebe stop at a pharmacy so Prue can purchase some aspirin. Phoebe tells her to quit fighting their destiny as the Charmed Ones, and that's when a bottle of aspirin goes flying off the shelf by itself. Realizing Prue's telekinesis is triggered by anger, Phoebe antagonizes her sister, mentioning first Roger and then their estranged father. Prue inadvertently makes all the products go flying off the shelves, but afterwards, actually feels better. Meanwhile, in an elevator of the abandoned warehouse, Jeremy tells Piper he has a surprise for her, remarking that she'll probably tell Prue and Phoebe all about it later. However, Piper points out that she never mentioned Phoebe was back, and that's when Jeremy pulls out an athame, Piper's 'surprise'. He explains he's been waiting months for Phoebe's return, knowing that as soon as Grams died and the sisters were reunited, they'd get their powers. Piper realizes he killed those other witches and asks him why, to which he replies that he was after their powers. He even demonstrates the pyrokinetic ability he stole from Serena. He then tries to kill Piper and take her power as well, but she ends up freezing him. As she attempts to climb out of the elevator, however, he unfreezes and tries to pull her back in, but she manages to grab a two-by-four and knock him unconscious with it. Later, at the Halliwells', Prue and Phoebe return home to find Serena's cat, Kit, has gotten in, just as Piper arrives and asks Phoebe about getting rid of a warlock. Back at the abandoned warehouse, Jeremy awakens, setting out to find Piper and her sisters.

Back at the Halliwells', meanwhile, the sisters sit around an altar in the attic, preparing to cast a spell. Piper uses a poppet and a rose with thorns to try to make Jeremy go away, but all it does is make Jeremy break out in rose thorns all over his skin. Phoebe receives a vision that Jeremy is on his way, and announces that the spell didn't work. So, she and her sisters head downstairs, presumably either to leave or to lock the front door, but unfortunately, Jeremy arrives just then and manages to corner the sisters in the attic. He traps them in a ring of fire, just as they remember the inscription on the back of the spirit board and begin chanting "The power of three will set us free" over and over. The spell seems to take effect, though Jeremy warns that more evil beings will come after them and that they will never truly be 'free'. Finally, he explodes in a burst of bright light, and is defeated. The next day, Prue goes to retrieve the morning paper, only to find Andy outside, waiting to ask her out. She appears reluctant, explaining that it's because her life has gotten "a bit complicated" lately. She does, however, ask if she can call him. So, he gives her his card and leaves, just as Prue's sisters join her outside. She wonders aloud if witches can date, then as they head back inside, discuss how life will never be the same. Once inside with her sisters, Prue uses her new power to shut the front door.