In P3, we see Piper, Leo and Prue standing at the bar when Phoebe walks up to them. Phoebe says that she doesn't think they're going to be able to make it to the movies in time, although Leo and her sisters reassure her that they have been in tighter jams than this before. Prue says her plan about how they can make it to see Faithless in time, but Leo says that he thought they were going to go and see a thriller, not a foreign film. Now that Piper and Leo are married, Piper refers to it as the power of four, where Piper and Leo vote together against Prue and Phoebe, coming out to a tie. Phoebe says that she doesn't want to see a thriller because she will be reminded of Cole and his demon-dodging. But, when Leo looks at the entrance to P3, he sees Cole coming down the steps and knows that Phoebe will want to spend time with him rather than watch a movie. Phoebe meets Cole halfway to the bar and they hug and then kiss. Cole says it's good to be back when they reach Leo, Piper, and Prue, and that he would rather spend some time alone with Phoebe than be the tie-breaker to a movie. Phoebe is fine with this and the two leave, meaning Prue is stuck watching the thriller.
Outside on the street, Phoebe and Cole are walking and just talking. Phoebe tells him that she almost didn't think he would make it back for her graduation, but Cole reassures her that he wouldn't miss it for the world or the underworld. Then she asks him if it is really safe for him to be here. Cole tells her that he thinks it is, although he is hesitant with the answer. Phoebe, sensing his hesitation, wants to know what is wrong. It is now that Cole comes out with it and says in a tired voice that he doesn't know how much longer he can keep running for, and suggests that he strips his powers so that he can be good, with no temptation to use his demoic powers, and the two can finally be together. Phoebe, amazed that he would be willing to give that much up to be with her, kisses him.
Down the street, an old homeless man begins to scream about THE BROTHERHOOD and warns that THE THORN is coming.
Cole, hearing this, is distracted and they stop kissing, turning his attention to the man. Phoebe doesn't know exactly what's going, but Cole tells her that he should watch what he is saying, just as a demon appears behind him and pulls him into an alley. Phoebe runs down the street to try to save him but finds him dead, although she manages to kill the demon that killed him. When Cole, who was obviously taking his time, gets to the alley, he tells Phoebe that she just vanquished his brother.
Now, back at the manor, Phoebe doesn't understand why Cole never told her that he had a brother, although Cole says that he isn't that kind of brother. After being called from their movie just before they found out who the real killer was in the thriller, Piper, Prue and Leo come home and enter the conversation, in which Cole explains that he is a member of "the brotherhood of the thorn", an elite gang of demons who answer directly to the Source. Phoebe now understands that it is simply another demon in the brotherhood that she vanquished. Leo fills the girls in on the brotherhood, and tells them that when you become a brother you take a blood oath and pledge loyalty until death. Cole then explains that the brotherhood must have something big in the works and would kill street preachers, some of which aren't human and others are seers, to make sure that no one finds out about their plans from the prophets. Leo tells the sisters that the brotherhood is way beyond anything they've dealt with before and it is going to take more than "a little research and your kick, freeze, magical move" (as said by Cole). Cole determines that the only way to figure out WHAT the brotherhood is up to, is for him to go back. Phoebe tries to convince him that it is a bad idea but Cole, being stubborn, will not give in so she just walks away.
At the Brotherhood's set up above ground, Vornac, a powerful demon and the assumed head of this section of the brotherhood, is told that Triggs, the demon Phoebe vanquished, is missing.
Up in the attic, Phoebe is trying to make Cole's power stripping potion so that he won't have to go. However, Cole insists on going and says he will need his powers while he is gone.
When talking, Cole reveals that the mausoleum is the second safest place he knows. When asked by Phoebe what the first safest is, he tells her "with you".
They agree to meet at the mausoleum in two hours. Cole shimmers out.
At the brotherhood's building, Klea, a demon, notices Cole/Belthazor walking towards the room they are in. Vornac is extremely upset with the fact that Belthazor left them and is convinced he is a traitor. Cole then tries to convince his brothers that he is back to help with their plan and is interested only in helping the brotherhood. Vornac asks Cole what he has that can save his traitoress head. Cole opens up a bag and drops the head of the prophet who was killed by Triggs onto the floor in front of Vornac. Still trying to get his way back into the brotherhood to collect information and make his brothers trust him, Cole is sticking to his story that he is there to help. Vornac, however, will not believe him so easily and isn't about to let Belthazor back in, rather than kill him. To explain why Cole killed the Triad, he says that they were plotting to kill the Source, along with any demons in his inner circle, including Raynor, who is the leader of the brotherhood. Klea is sent to check Belthazor's story. Until Klea comes back with information proving his story either way, Cole is not trusted. He does, however, catch a glimpse of what is on the television screen, being someone at Pier and Pescadero Street at 8 AM.
Meanwhile, at the manor, Piper, Prue, and Leo found that Frank Pirelli, owner of Lexserom - which the prophet mentioned - did not want a big merger to pass that would make all of the world's information go through one company. Leo then orbs to the mausoleum to check on Phoebe and see if she has heard from Cole.
When Cole shows up at the mausoleum, he says that he has to be quick, but he and Leo swap information and agree that the brotherhood is after Pirelli because they want a merger to go through in order to take over businesses in the human world and get a foothold. Cole tells Phoebe that he is looking forward to seeing her in her cap and gown, and shimmers out.
At the brotherhood's building, Cole walks back into the office carrying a water bottle that he borrowed from Phoebe and says that he got thirsty. The brotherhood reviews their plan, but Vornac changes one thing - rather than having another demon throw an energy ball at Pirelli's car, Belthazor should do it to prove that he really is back. The only way they will believe him is if he kills.
On the corner of Pier and Pescadero, the brotherhood is setting up so that a car will be blocking Pirelli's limousine when an energy ball will be thrown.
Down the street, the sisters and Leo are on their way.
Klea returns and tells Vornac that she is unable to prove Belthazor's story as true or false. When the wheels of the plan are set in motion, Cole is told to throw the energy ball. Waiting until the last second to give Phoebe, Prue and Piper the most time he could, he throws it at the limo. Piper, just turning the street corner, freezes the scene before the car is hit. Leo hops into the back seat and orbs Pirelli out. The sisters begin to leave, until Phoebe slips a piece of paper into Cole's pocket. Piper unfreezes the scene and it looks as if Cole did what he was told. Klea is told to retreat the body of Pirelli, while Cole just now sees that Vornac's plan is to shape shift into Pirelli and to vote as Pirelli in agreeing to the merger. When Klea comes back without a body, she and Tarkin, another brother, are slightly suspicious as to why there was no body in the car.
Back at the manor, one of Phoebe's great potions has put Pirelli to sleep, and the sisters are keeping him in the basement to protect him. When Prue turns on the TV to see if, what they thought was a kidnapping made the morning news, only to see the fake Pirelli on the TV, holding a press conference and stating that he has changed his vote and that the merger will happen. It is now that Piper is even more convinced that Cole has turned, seeing as he is back with his brothers, although Phoebe is still standing her ground in saying that if Cole would have known about the switch, he would have told them about it. When Piper doesn't stop talking badly about Cole, Prue, surprisingly enough, stands up for him and says that he has done a lot of good since then and that the sisters should give him the benefit of the doubt. Phoebe thanks her for this. Piper and Phoebe continue arguing about whether or not Cole has betrayed them, while Leo checks on Pirelli and confirms that he is still out cold in the basement. Prue, once again, steps up as mediator between the two sisters, and attempts to get them on the track of figuring out a new plan. It is now that Phoebe tells her sisters that she is going to try to get Cole to meet her, and about the note that she slipped him when he was frozen at the attack, saying to meet her at the mausoleum. Prue tells Phoebe to go and be careful, and to come back right away if Cole doesn't show up so that they can work on a plan B. Phoebe leaves. When Piper is stumped as to how they have a plan B, Prue tells her and Leo that part of it is in the freezer. Going into the kitchen, Piper is skeptical of what in the freezer could help in this situation, then turning disgusted when she sees Prue pull out a container with the old piece of Belthazor flesh in it. The way Prue sees it, if the members of the brotherhood all took a blood oath, that means it is their blood, so a vanquishing potion to kill one, being Belthazor, should work on them all. Prue now admits to keeping the piece of flesh because in the back of her mind she thought she might need it someday, or in other words, that Cole would return to being evil.
At the brotherhood's office, Cole notices the note in his pocket and quickly reads it, just before Vornac disguised as Pirelli and Klea show up. After hearing talk from Klea of no body being recovered in the car, meaning he somehow got out; he believes it to be impossible, although Klea is not so sure. She then suggests that it was done magically. Not turning to Belthazor, the number one suspect for being a traitor, Vornac, no longer in disguise, questions Cole. With nothing else to say that would be smart, Cole simply says that he agrees with Klea and that someone interfered with their plan. Vornac, persistent to find the reason why his plan could go up in flames, asks Belthazor who could have done it…he says perhaps witches…and how they could be onto their plan. Belthazor now suggests that they may have a leak. Slowly moving closer to Cole, he asks him who their leak could be, but Tarkin cuts in, sticking up for Belthazor. During this interrogation, Vornac begins to talk about the disturbing rumors he heard while Belthazor was on the run, speaking of Cole's love for Phoebe, and the coincidence that now they are confronted with the possibility that their entire plan may be jeopardized because of witches. All of the brothers are in shock when Cole admits to having loved Phoebe, or at least his human half, although he denies loving her anymore. He tells his brothers that he may be able to get Pirelli back, and tells them of Piper's power to freeze, which could have easily interfered with the operation and they wouldn't even know it. Vornac, being lenient, gives Belthazor the chance to redeem himself, and allows him to go to Phoebe and try to get Pirelli back, although he is still suspicious and sends Klea to follow him, telling her to help him if he is actually saving them or kill him if he isn't, to kill him. Klea disappears.
At the mausoleum, Cole shimmers in to meet Phoebe like her note suggested. However, knowing that he could have been followed, Cole keeps Phoebe at a distant and almost acts mean or evil, not like a demon that is in love. Cole asks where Pirelli is, and Phoebe tells him that he is in the basement, and asks her plan, being to vanquish Vornac before the vote. Cole tells her that vanquishing Vornac would be a huge mistake, warns her to be scared because she doesn't know what she is up against, and tells her to go home and wait to hear from him. Then he shimmers out.
When Phoebe gets back to the manor, she tells Piper and Prue about the way Cole was acting. She says that he was acting strange, almost mean, and that he doesn't want them to go after the demon. When Phoebe says that she thinks she is in trouble, Piper again brings up the idea that he has turned. After Phoebe tells them that she trusts Cole isn't evil, three demons appear, which the girls fight off until Leo comes to them with two vanquishing potions made from the Belthazor flesh, which they use to kill the two remaining demons. Phoebe, confused and unaware that they had any potions, is amazed to see the potions work. Prue, noticing that this was way too easy, realizes that it was just a distraction, and runs to the basement with Phoebe, Piper and Leo following her. As the group runs down the steps, they get there just in time to see Cole and Tarkin shimmer out with Pirelli. Piper asks Phoebe what she thinks about Cole now.
Back upstairs, Phoebe is upset that Prue kept some of the vanquishing potion, meaning that she didn't really trust Cole. Despite what Piper thinks, Phoebe is still reluctant to think that Cole has turned, and believes this is all part of his plan, somehow. Piper, Prue, and Leo are getting ready to leave and go to vanquish Vornac, despite what Cole said, and Phoebe is asked if she will come.
Back in the brotherhood building, Vornac is ranting about what went wrong at the manor that would cost him three of his best demons. Tarkin tells him that the witches were more prepared that they counted on, and Vornac assumes that they must have been told about the demons' coming to the manor by Belthazor. Cole tells him that he didn't tip them, so Vornac turns to Klea for information. She tells him that Cole told Phoebe to go home, and proposes that it was a code. Cole swears that it wasn't, and tells them that his plan worked, and that he has Pirelli back, although he decides to use Pirelli as lee-way so that he doesn't get killed. When it is almost time for the merger vote, Vornac is about to shimmer out, but Cole stops him. He warns Vornac about the witches having the vanquishing potion to kill him and their motivation to do it, especially now that they've kidnapped Pirelli. Interested by this, Vornac asks Cole a rhetorical question: But will they vanquish you (Cole)?
In a corporal office, Piper, Phoebe, and Prue walk in. They suspect to see Vornac, or the shape shifted version of Pirelli sitting at the chair at the end of the table, but when the chair spins towards them, they are surprised to see Cole. After Piper and Prue make it clear they aren't working with him, and Phoebe kind of standing in the back silently, Cole tells them that Pirelli is somewhere safe. After being asked again, Cole says, where else would he be? Phoebe now comes into the conversation, saying…the safest place you know, the mausoleum? Cole asks her, isn't that what we agreed to, surprised to hear Phoebe say no, and throw the vanquishing potion at him. Cole starts to yell in pain, and then he changes back into Vornac, and is vanquished. Piper, surprised that Phoebe would take a risk, asks Phoebe how and if she knew whether or not that was Cole. Phoebe, repeating what Cole told her earlier, tells them that the safest place Cole knows is with her. Cole shimmers in behind them, almost being vanquished due to catching the sisters off guard. He explains that he had to play it this way, to avoid being caught as a traitor and being able to collect information, and had no other choice but to convince his brothers that he was evil by making the sisters believe he was evil, too. Piper tells him that she still thinks he is evil, although Prue, not being so direct, asks why Vornac impersonated him. Cole tells them that Vornac wanted to see whether or not he was a traitor and wanted to find out whose side he was really on. Turning to Phoebe, he tells her that he had to make her think he betrayed her and asks for forgiveness. Phoebe tells him that she never doubted him, but maybe just a little and they kiss. In the plants near the door, Klea's eyes are watching Cole and Phoebe kiss, see this, and they disappear. Cole tells them to get Leo to get Pirelli out of the mausoleum before the merger, and that he would do it himself if he didn't have to go to the brotherhood to cover his tracks. By the look on Phoebe's face, he can tell that she doesn't like the idea of him going back now, although she is eased by his comfort, and a promise that he will be at her graduation party that night. He shimmers out.
Back at the brotherhood building, Cole and Tarkin are talking. Cole tells Tarkin that he saw what was left of Vornac after the witches vanquished him, so he went to retrieve Pirelli at the mausoleum, but he was already gone. Tarkin then tells Cole that Raynor wants a full accounting of what happened. Cole tells Tarkin to tell him that he warned Vornac not to go but he didn't listen, and that now, he has to go. Taken back, Tarkin asks where he is going. Cole, being demon of the century with a few aces up his sleeve, tells him that he has to go and find proof for the Source to clear his name, which he can't do in the brotherhood's building. Tarkin tells him that Raynor wants a full accounting from him, Belthazor, but Cole is not okay with that idea and tells Tarkin that they both know just as much to tell Raynor. On his way out, Cole is hit from behind with an energy ball by Raynor, who just appeared with Klea, who told him of what she saw. Raynor tells Tarkin that Belthazor has much to explain and much to answer for.
Later that night at Phoebe's graduation party, that's being held at P3, Cole has not yet shown up like he promised, and Phoebe isn't celebrating because she's too worried. When Prue tries to tell Phoebe that no matter what happens, he (Cole) did the right thing, and that he helped get Pirelli back and the sisters stop the brotherhood, and Piper tries to help her cheer up by saying that Cole proved he was good, Phoebe shows her pain and worry for Cole. She asks, but at what cost? Shouldn't I get to protect one part of my life and say this…magic doesn't get to screw with, this I get to keep? She tells them that last night, Cole was back and he wanted to strip his powers, and she was graduating. She tells them that yesterday, everything was perfect, and now it's all fallen apart. To end the episode, Phoebe asks two simple questions: Where is he? What happened to him?