Phoebe walks into the darkened manor and calls for her "sister witches", only to find Piper on the couch with Rob, a loan officer. Piper freezes him and scolds Phoebe for speaking of witches. Phoebe hadn't known that a man was in the house. Prue walks in and Piper shoos her out before unfreezing Rob. Rob agrees to meet Piper at the club she is trying to buy. Phoebe proposes to go to an autumnal equinox celebration, a powerful day that is also their first anniversary of becoming witches.
The Book of Shadows flips, and the page says "Rite of passage: fight it with the Power of One or else" but Phoebe cannot finish reading it before a demon opens a portal in the attic and draws the Book to him. Piper thinks the "Power of One" refers to Prue, as she has the strongest power. The doorbell rings and Jenny Gordon steps in. She wants to use the phone and is trying to reach her parents in Saudi Arabia. Dan Gordon, her uncle, steps in behind her; the two are not talking, but he persuades Jenny to leave.
The demon chants strangely over a page in the Book of Shadows, and the writing disappears.
Phoebe and Piper go to the equinox celebration. About a dozen other young women have gathered around a stone altar. The others all disrobe, but while Phoebe is enthusiastic, Piper is embarrassed. Phoebe hears Grams saying, "The Power of Three", but Piper does not.
Piper drives up to the club and finds Rob already there. Rob says that running a club is risky, but Piper convinces him to grant the loan. Meanwhile, the demon chants over the Book and Jeremy Burns reappears. Grams says "The Power of Three" to Piper just as Jeremy blinks into the club and knocks Rob to the ground. Piper freezes him and conference-calls Prue and Phoebe. But Jeremy unfreezes, and Piper can't freeze him again despite several attempts. By way of speaker phone, they say the spell to vanquish Jeremy.
Rob is in a gurney being readied to go to the hospital, and suggests the crime level in the area could jeopardize the loan. Prue comes to check on Piper, and Piper tells her how she heard Grams.
Phoebe hears Kit meowing outside and finds Jenny holding her. Phoebe starts talking to Jenny. Phoebe, for the first time, notices the triquetra on Kit's collar. Phoebe leaves as Piper drives up, with Kit in her arms, and shows the triquetra to Piper. She thinks this is some kind of symbol of the Power of Three. The two consult the Spirit Board, and Grams says "The Power of Three" again--this time Piper hears it. The Spirit Board spells out "Abraxas". Phoebe finds Abraxas in one of several occult books she has bought; he is a demon of the astral plane that demonizes the powers of good witches.
Abraxas chants over another page of the Book and the Woogyman appears in the manor. The two sisters scramble to remember the spell to vanquish the Woogyman. Piper remembers that the spell to vanquish Jeremy was in the back of the book and that for the Woogyman before it; Abraxas is reading the Book backwards. Phoebe has a premonition of Nicholas killing Prue.
Prue is talking to a customer when Nicholas appears in the hall. Prue escapes into her office, but Nicholas follows her in before she can close the door. He uses his ring to heat Prue up from within. Prue, with difficulty, speaks a spell and Nicholas is vanquished just as Prue falls over unconscious.
Piper and Phoebe visit Prue in the hospital. Phoebe believes the Book is still in the attic, but within the astral plane. She also realizes that if Abraxas reaches the start of the book, they will lose their powers, because the spell that gave them their powers is at the very beginning. Prue, feeling responsible for Andy's death, wants to stop being a witch.
Rob's assistant tells Piper that the loan has been denied.
Prue goes to Darryl and wants to know how much Andy told him about who the Halliwells really are. Darryl says only that he knows they were connected to some unsolved cases and that they somehow help stop killers. He also tells her that Andy told him to tell her that if anything happened to him, it wouldn't be her fault.
The sisters go to the attic and Piper draws a large triquetra on the wall. Prue arrives from the station. The sisters plan to get the open a portal in the astral plane, then Prue will knock Abraxas away from the Book while Piper and Phoebe grab it. Piper and Phoebe aren't sure Prue is up to it, but Prue reassures them by moving a chair. The sisters open a portal in the triquetra, but Prue freezes up and cannot knock Abraxas away from the Book. Abraxas flings them across the room. Phoebe and Piper scold Prue, and she breaks down and cries over Andy. She blames herself for Andy's death. The other sisters tell Prue that Andy had chosen to walk into the manor. As the sisters embrace, Grams whispers again; only this time, all three sisters hear. They determine that the "Power of One" is the three of them working as one.
The three sisters return to the stone altar at sunrise and chant the spell that invokes the Power of Three just as Abraxas is reading the same spell backwards. The Book pops out of a portal onto the altar. The sisters continue to chant and a portal appears, revealing Abraxas. Abraxas is drawn into the altar and disappears into a large glowing triquetra.
The Rite of Passage page reads in full: "Rite of passage: fight it with the Power of One or else...a more powerful Evil that awaits will destroy you."
Prue and Phoebe have taken out a second mortgage on the manor so Piper can buy her club, with her sisters as partners.
Grams whispers once more, and then appears in ghostly form. It turns out that when the Book turns itself, it's Grams doing the turning. After she disappears, the Book turns once more. The page reads: "Happy Anniversary, my darlings."