A stormy night and a full moon finds a woman, Serena Fredrick, alone in her apartment with her cat. She has arranged a number of candles on an altar; she lights each candle by merely pointing at it. She chants an incantation as a man skulks outside. The man sneaks in and stabs the woman.
Piper Halliwell rushes in from the rain after a job interview while her older sister, Prue, is trying to fix the chandelier. Piper's boyfriend, Jeremy Burns, sent her a bottle of port; Piper thinks it's just what she needs to win a chef's job at a restaurant. Piper spots their old spirit board sitting on the table; Prue found it earlier. It has a cryptic message on the back from their mother, saying that "The Power of Three will set you free". Prue suggests that they send it to their younger sister, Phoebe, thinking it'll help get her out of what she sees as her current aimless path. Piper thinks Prue is being too hard on Phoebe, and thinks she's coming around. The pointer on the spirit board moves, unseen by Prue and Piper.
Inspectors Darryl Morris and Andy Trudeau investigate the woman's murder. Andy tells Darryl about witches, but Darryl isn't willing to listen. Jeremy, a reporter for the Chronicle, appears and asks them about the murder.
Prue mentions that she's thinking of renting out a room in return for help with the chores. Just then, Piper tells Prue that Phoebe is moving back in from New York. Prue is angry with Phoebe because she thinks she tried to steal her ex-fiancé Roger, but Phoebe has nowhere else to go. Prue asks when Phoebe is to arrive, and at that moment Phoebe comes through the door. Piper and Phoebe embrace, but Prue thinks Phoebe is trying to get them to sell their house. Piper offers to make a reunion dinner, but Prue and Phoebe both pass.
Phoebe settles into her old room when Piper brings her a snack. The TV carries a report on the murder, and they see Jeremy on it, who turns out to be Piper's boyfriend. Phoebe wonders why Piper didn't let Prue know sooner that she was coming home, but Piper was afraid Prue would change the locks. Phoebe would have asked, but she and Prue didn't get along that well even before the blowup over Roger. Prue comes in and drops off some extra blankets, claiming that Phoebe's room is the coldest one of the house.
Andy and Darryl find a triquetra tattoo on the murdered woman's neck. Darryl is skeptical about witches, but notes the "freak fest" that the woman was engaged in.
Piper and Phoebe play with the spirit board. The pointer, held by Phoebe, moves on its own, first to "A", then to "T". Prue and Piper think Phoebe moved it; she had a habit of moving the pointer when they were younger. Just as Prue and Piper walk away, the pointer moves again, back to "T". Prue still thinks Phoebe moved it. Before Piper can turn around, the pointer moves again--first to "I", then to "C". Phoebe realizes the letters spell out "attic". Just then, all the lights in the manor go out.
Piper is frightened out of her wits and wants to go to Jeremy's place to wait out the storm. She's convinced the pointer moved, but Prue thinks Phoebe was playing a joke on them. While Prue and Piper go to check out the circuit box, Phoebe goes to the attic. She can't get the door open, but as she walks away the door opens on its own. Inside the attic, Phoebe sees a beam of light illuminating a trunk. She opens the trunk and finds a large book within. She opens the book and finds its title: "The Book of Shadows". She reads an incantation from the first page. Light appears within the attic, the chandelier starts shimmering, and a photo changes, bringing the images of the sisters closer together. Piper and Prue come into the attic and Phoebe tells them about the Book. However, the sisters don't think anything really happened.
Come morning, Phoebe tells Piper she spent most of the night reading in the Book. They are descendants of Melinda Warren, a powerful good witch who was burned at the stake during the Salem Witch Trials. Melinda could freeze time, move things with her mind and see the future. While at the stake, Melinda prophesied that every succeeding generation of Warren witches would grow more powerful, culminating in the arrival of three sisters who would be the most powerful witches in history—the Charmed Ones. Phoebe believes that she, Prue and Piper are those sisters. Piper is skeptical.
Prue's boss at the American Museum of Natural History, Roger (who is also her ex-fiancé), has taken her off an exhibit even though Prue secured most of the pieces. Prue realizes that Roger has appointed himself as the new curator. Prue curses at him and walks away. A pen in Roger's shirt pocket explodes and leaks; he pulls the pen out and it sprays him in the face.
At the restaurant, Piper is working on a recipe when Chef Moore enters. Just as he is lecturing her about the quality of her work, Piper raises her hands. Without warning, Chef Moore freezes; Piper applies the port sauce to a sample that Chef Moore is tasting. Chef Moore unfreezes just as he's tasting the meal, and is suitably impressed. Piper tries to call Phoebe during her break to tell her what happened, but can't reach her. As she gets out of the booth, Jeremy surprises her and asks her out on a date.
Prue goes to Roger and announces she's quitting. He taunts her as she walks away and she gestures; Roger's tie chokes him and he frantically grabs a pair of scissors to cut it.
Phoebe is riding her bike when she has a vision of two young men on roller skates being hit by a car. She then sees the car and the two young men and swerves, diverting the two young men out of harm's way but taking a spill on her bike and hurting her arm. Prue comes to the hospital to fetch Phoebe and bumps into Andy; he turns out to be an old boyfriend.
Prue meets with Phoebe at a restaurant. Prue still doesn't believe she has powers, until she wonders where the cream is for her coffee and it slides over to her and fills her cup. Phoebe thinks that if she can see the future and Prue can move things with her mind, Piper can freeze time. Prue is slightly annoyed at Phoebe, thinking she turned her into a witch. Phoebe explains that they were born as witches. On the way to the pharmacy, Phoebe mentions that witches can be either good or evil, and that warlocks are evil witches who kill good witches to obtain their powers.
Piper and Jeremy just ate Chinese and are on their way to Jeremy's place. Suddenly, Jeremy asks the taxi driver to take them to an old building with a great view of the Bay Bridge.
At the pharmacy, Prue complains of a headache. She still isn't happy about finding out she's a witch. Phoebe suggests that Prue move her headache out of her mind--and a bottle of aspirin flies into Prue's hand. Phoebe realizes that Prue moves things when she's angry. Prue doesn't believe it at first, but Phoebe provokes her by mentioning Roger causing two more bottles to fly off the shelf. Phoebe then mentions their father and the shelves collapse, sending Prue and Phoebe into laughter.
Piper and Jeremy enter a warehouse and board a freight elevator, promising her a "surprise". On the way up, he mentions that he knew Phoebe was back in town. Just as Piper wonders how Jeremy could have possibly known this, he pulls out his surprise—an athame. Jeremy is the warlock who killed the witch at the start, and three other witches in the past few weeks. He has known all along that Prue, Piper and Phoebe were magical, and had been waiting for them to discover their powers. Piper screams and raises her hands; causing Jeremy to freeze. Piper tries to flee, but Jeremy unfreezes and grabs her by the leg. Piper cracks Jeremy over the head with a piece of wood and escapes.
Piper arrives at the manor and warns her sisters about Jeremy. Phoebe consults the Book of Shadows and the sisters cast a spell to make Jeremy go away. All it does, however, is sprout thorns from his skin. Phoebe touches a pot used in the spell and realizes, from a premonition, that Jeremy is still after them.
Jeremy appears at the manor just as the sisters are heading out the door. Piper and Phoebe flee to the attic; Prue tries to slow Jeremy down by flinging him against the wall and joins her sisters upstairs. The sisters bar themselves in the attic, but Jeremy uses psychokinesis to unbar the door, and then uses the pyrokinesis he stole from Serena to blow open the door. Prue remembers the inscription on the spirit board. As Jeremy starts a circle of fire to destroy the sisters, they start chanting, "The Power of Three will set us free." Jeremy taunts the sisters as they chant, warning them that he's the first of many evil beings they'll encounter, and eventually explodes.
The cat has now taken up residence at the manor.
Andy shows up at the manor the next day and asks Prue out. Prue demurs, saying her life has gotten "complicated." Piper and Phoebe listen in. Prue tells them she doesn't know if witches can date. Piper says that witches usually get the best guys. Andy notices Phoebe is holding the cat, and casts a skeptical glance before heading out. Prue reminds them that everything will be different from now on, and that they have to stick together. As the sisters head back into the manor, Prue winks at the door, and it swings closed behind them.