A woman, Katrina, is feeding her cats, when a warlock blinks in. She senses him and attacks in self-defense. Blinking behind her, she turns around and he cuts a necklace off her neck, but she kicks him down and signals the cats to attack him. Katrina escapes, but the warlock fights off the cats and he picks up her necklace. It bears a triquetra.
Paige and Phoebe are talking about Piper's past relationships. Leo and Piper are arguing. Leo is walking away and Piper accidentally blows up a door in her anger. This worries Paige and Phoebe. Phoebe and Paige try to help them work it out. But Leo insists that it's not their problem. Phoebe schedules Leo and Piper to see a mortal marriage counselor, with Paige explaining that their problems are marital, not supernatural. They both agree.
The warlock is looking through a drawer, when he finds a scry crystal and a map. He scries for Katrina and finally, the scry crystal lands on a location. Paige goes to Phoebe's work and tells her that she's been worried about Piper and Leo. Phoebe agrees, saying that she's been feeling the same way too. But she reassures Paige that they've been through a lot worse. Katrina calls Phoebe and says a warlock is after her. She is in the manor, asking for her to come home with her sisters and Leo, because she has a cut across her neck, and she needs healing. Leo, however, is with the marriage counselor.
Leo and Piper meet with the marriage counselor. They are sitting at opposite ends of the couch. They talk a little and when the marriage counselor asks for a history of their childhood, Piper freezes him, thinking that it will take months. Piper casts a memory spell and unfreezes the counselor. She tells him that they should just skip the childhood part, with Leo agreeing.
The warlock is attacking Katrina to the manor, but Paige and Phoebe orb in. Paige orbs Katrina away, while Phoebe struggles and fights the warlock. Phoebe gets the upper hand, but she, Paige and the warlock suddenly find themselves outside the manor. The warlock blinks away. Paige and Phoebe suspect that the warlock blinked them outside the house.
As Leo and Piper retell their past experiences in an effort to rekindle their love for each other, Phoebe and Paige find themselves watching those same experiences play out. They see a flashback of Phoebe checking out Leo. Paige is confused and Phoebe says that it's her from about 5 years ago. Paige is disgusted that Phoebe has hit on Leo before. They find themselves in the attic where Dantalian is stealing the Book of Shadows. They stay hidden and see past-Phoebe and past-Piper torturing Dantalian. They also see them literally freeze Leo and shatter him to pieces. Paige and Phoebe try to orb out, but they are "bounced back".
Piper and Leo continue to talk, then, the marriage counselor asks them to talk about their wedding. Paige and Phoebe are flashed to the scene of Leo and Piper's wedding (Prue briefly appears in this scene in footage reused from Just Harried), and after Kit, their cat, comes up to them, the warlock blinks in. He seems as surprised as Phoebe and Paige and quickly blinks away again, after stepping on Piper and Leo's wedding cake topper. Phoebe and Paige fear that the warlock has altered the past.
Piper feels a sharp pain in her heart and the cake topper from the present-day disappears. Paige and Phoebe soon realize that none of the flashbacks are the warlock's doing and that since all of the events are centered around Piper and Leo, they think that it may be Piper's doing. In the middle of potion-making, they are flashed into the scene where Piper, for the first time, really admitted her love for Leo. They see Piper finally being able to heal Leo, realizing that the trigger to heal was love.
Kit comes up to Paige and Phoebe again and the warlock blinks in and then blinks out again. They then realize that the warlock was after Kit, not them. After reading the Book of Shadows entry on familiars, they realize that Kit had been their familiar.
Back at the marriage counselor, Leo upset about Piper not thinking he's good enough and thinking he has codependency issues. The marriage counselor asks for a memory that they've overcome as a couple. They are flashed back into the memory of Piper and Leo's first kiss. They are flashed into another memory of Piper outside P3, waiting for Leo to be returned to her. They are then, again, flashed into another memory of Prue (as a dog) chasing Kit, just around the time Piper has developed her new exploding power. They are also flashed into another memory of Leo saving Phoebe and Piper from the knight, when Paige's past life trapped them. They are then flashed into the memory of Phoebe accidentally walked in the bathroom while Piper and Leo were taking a shower and kissing which turns out was future Phoebe. They then get flashed into a memory of when Piper was possessed by Terra and was table dancing at P3. They are then flashed into the memory of Leo's proposal to Piper. Kit starts yowling upstairs so Paige orbs to find the warlock has just stabbed Kit. Kit's corpse morphs into that of Katrina. In the present, Katrina disappears.
Leo develops a sudden headache; he's feeling the pain of hundreds of witches who weren't able to protect themselves, because of not being able to be helped by Kit in the future. Piper freezes the marriage counselor and strangely hears Phoebe calling to her from the past. Phoebe wants Piper to go back to when Leo proposed to her so that they can change the past. This time, Paige and Phoebe are ready for the warlock. They get to the attic before the warlock gets to Kit. Paige throws the potion, making him unable to blink. Phoebe stabs him, vanquishing him.
Katrina has reappeared and reveals that she had been Kit, and that she'd left, because her work with the Charmed Ones had been complete. Leo says that the Elders had made her human to guide other familiars--a reward granted to only a few special familiars. He also reveals that the pain he'd felt had been those of the witches who'd lost the familiars Katrina had been training when she'd been killed by the warlock. Katrina requests that they call her when Wyatt comes into his powers, with Piper agreeing. Piper and Leo vow to spend more time together. At the end of the episode, however, it is revealed that the wedding cake topper is still missing.