The next morning, the Siren is seducing a man on a bed with her song. She tells him that his wife is almost there and then she can watch him die. As the wife comes into the room, the Siren kisses that man. He begins to turn gray as smoke rises off his lips. He falls back dead on the bed. The wife, Melissa, walks in, obviously in a trance. The sight of her dead husband snaps her back to herself. She tries to revive her husband, but to no avail. The Siren starts a fire in the room, telling her she was burned to death and the new widow should die that way as well. She smokes out.
Almost at the same time, Cole is still trying to talk Phoebe into getting back with him, but Phoebe is determined to go through with the divorce. Cole also tells Phoebe of some of the good deeds he's done, but she is still convinced that at bottom he's a demon. While they are talking, Cole sees the burning building and fades there and pulls Melissa out of the flames. Phoebe looks at the television and sees Cole walking out of the building with the unconscious woman.
Back at the manor, Paige is concentrating on making her potions. Piper is upset that her baby is making her burp orb-like bubbles, along with other tricks that it has been playing on her recently combined with nausea and breast pain. She's somewhat upset that Leo hasn't been paying attention. Piper and Paige go to the living room and find Leo watching news of Cole rescuing the woman. Paige isn't impressed, but Leo mentions the woman, Melissa, is a future Whitelighter. Piper tries to ask Leo about the tricks the baby is playing on her body. However, Leo has to hurry out to protect Melissa. Piper is upset that Leo doesn't understand what's happening to her. Paige wonders if a Darklighter is after Melissa, but Piper isn't so sure; Darklighters usually don't burn people to death.
Elise wants Phoebe to get an exclusive interview with Cole. Phoebe thinks it's too awkward, but reluctantly goes along.
The Siren runs into a man at a bar. She hums a song and starts to come on to him. Suddenly, she sees the footage of Cole saving Melissa and leaves in a huff.
At Phoebe’s office, Cole tells Phoebe that he feared he'd never see her again if he died in the fire; he is still very much in love with her. Phoebe, however, tells him that while he may be the toast of the city, she's scared to death of him because he has more powers than any demon she's ever faced. She thinks that despite her attempts to save him, the evil in him is simply too strong. Cole wants to prove that he's good. Phoebe tells him that as much as he wants to believe he's good, it's only a matter of time before he gives in to evil again. Cole walks out.
Paige has summoned a Darklighter and trapped him in a crystal cage, much to Piper's alarm. She found out that Melissa wasn't attacked by a Darklighter, but Paige still isn't buying it. The Darklighter gets out of the cage, and he conjures his crossbow. Piper tries to blast him, but only starts a small fireworks display over him. Paige orbs the crossbow into her hand and kills the Darklighter with it. Piper realizes the baby's pacifist tendencies are messing with her powers. She calls for Leo and he responds on her cell phone from the hospital. He's trying to get a window to heal Melissa. He hurries back to Melissa's room, much to Piper's frustration.
Just as Leo gets to Melissa's room, the Siren smokes in. She spots his wedding ring and sings to him. Piper hears the song as well. She and Paige orb to Melissa's room just as the Siren is kissing Leo. Paige cracks the Siren over the back with an IV stand. While she's distracted, Leo orbs Melissa out. Piper tries to blast her and covers her with flowers. The Siren flings Piper through a window. Paige throws a pole at the Siren and impales her. She then guides Piper into a dumpster.
Piper and Paige orb back home just as Leo is healing Melissa. Piper freezes the room so she can talk with Leo. While Leo wants to figure out what's going on with Piper's powers, Piper is upset that Leo hasn't been with her more. Paige walks in; she's found the Siren in the Book. She is a demonic seductress who was once a mortal woman. She was burned at the stake for adultery while the married man she seduced got off scot-free. The woman's rage consumed her humanity, and turned her into a demon who seduces married men--only to burn him on the inside and then set the woman afire. However, Piper and Leo are still arguing, unaware that orbing lights are coming out of their backs. Suddenly, they're knocked to the ground. The room unfreezes. Piper tries to freeze Melissa again and instead briefly orbs. A frightened Melissa runs for the door. Leo tries to reach out to her, and blows out the glass. Melissa runs out the door just as Phoebe comes in.
The Siren goes to a demonic healer to fix the wound in her stomach. When the healer finds out she faced the Charmed Ones, he's skeptical about her going after them again. However, the Siren thinks that even though they're powerful witches, they're just like ordinary women when love is involved.
Phoebe realizes the baby switched Piper and Leo's powers because they haven't been talking lately and won't switch them back until they understand how the other one feels. Piper is getting a headache from hearing the voices of Leo's charges in her head. Cole fades in and warns everyone about the Siren. Leo burps an orb-like bubble, and is feeling nauseous and sore in an area where breasts would be in a woman--apparently he's having Piper's pregnancy symptoms, though the baby is still in Piper's womb. Cole thinks Phoebe's powers might be off as well, and offers to help them hunt down the Siren. Phoebe declines, and Cole fades out. Phoebe starts to wonder if she's being too hard on Cole, but Paige isn't so sure. Piper senses Melissa is overwhelmed. Leo offers to go, but Phoebe tells him Piper has to since she's the Whitelighter. Piper and Paige orb out, while Phoebe and Leo stay behind to make the vanquishing potion.
Piper and Paige find Melissa, but she's still not willing to talk to them. Piper hears another charge in trouble, and orbs to her. The charge turns out to be in Paris, France and Piper, much to her surprise, is able to speak to her in French.
Leo is still trying to get a handle on Piper's powers, and wonders how Piper pulls it off every day. Piper orbs in with a rooster in hand, and wonders why Leo never told her he spoke French. Leo tells her that Whitelighters have the ability to speak whatever language their charges speak. Piper is surprised; Leo never told her this before. Leo wants help using Piper's powers, but Piper hears another charge in trouble and orbs out. Phoebe needs Leo's help to summon the Siren.
Cole has found the Siren's lair, and is roughing up the healer when the Siren starts singing to him. Cole drops the healer and comes over to kiss the Siren. However, the Siren wants to lure Phoebe as well.
Leo has written a spell to summon the Siren to the manor, but Phoebe doesn't like the first draft. Paige orbs in and says Melissa got herself arrested. Piper orbs in; she sensed Melissa was in trouble, but can't pick her out from all the signals she's getting. Phoebe hears the Siren's song; apparently her love for Cole is stronger than she's letting on. Paige doesn't think she's good at being a Whitelighter, but Piper thinks her Whitelighter half made her study social work in the first place. Leo and Piper convince Paige to go back to Melissa. Paige finally manages to gain Melissa's trust.
Phoebe disappeared without any warning, and Piper is finding it hard to sense her. Figuring Cole somehow has her, she orbs herself and Leo to Cole's apartment. However, the apartment is deserted. Leo suggests Piper try sensing her again.
The Siren is about to kill Cole when Phoebe arrives. The Siren throws Phoebe into a wall, but Phoebe recovers, pulls out the potion and throws it at the Siren. Suddenly, Cole disintegrates it, saying he wants to finish the Siren off himself and then starts kissing her.
Piper is still having no luck sensing Phoebe, and wonders how Leo does it every day. Leo tells Piper that her love is the only thing that keeps him sane amid all of his Whitelighter duties. Piper finally senses Phoebe, and she and Leo orb to the Siren's lair. They arrive to find Cole choking Phoebe. Leo blasts the Siren backwards. Piper tries to pull Cole off Phoebe, but he knocks her across the room. Leo tries to blast the Siren again, but misses. Cole chokes Phoebe into unconsciousness. Leo manages to blow up the Siren, and Cole lets go of Phoebe. Piper heals Phoebe. Cole can't believe what's happened, and fades out.
The next morning, Piper and Leo apologize to one another for thinking that the other didn’t understand what they were going through. They both realize that they have a lot on their plate, but that together they can accomplish it all. After this, the baby switches back their powers. Paige is glad she finally got in touch with her Whitelighter side.
The next morning, Cole sends Phoebe some flowers to apologize, and also comes to her office to personally apologize to her. He tells her that he never meant for that to happen. Phoebe knows that the Siren's magic made him do it, but thinks this only proves their relationship is too dangerous to continue. Cole leaves feeling defeated, but not giving up hope.