A powerful ancient warlock, Aames, is killing off good witches and stealing their powers. A "Whitelighter," Natalie, warns the Charmed Ones and Leo of Aames. They find out that the warlock has the ability to clone himself, deflect the powers of others, and to shape shift. While Natalie decides to check in with the Elders, the Charmed Ones decide to go after Aames. The girls find him and begin to fight, but a "Darklighter" appears, Aames kills the "Darklighter," steals his crossbow and disappears. Back at the Manor, Natalie, being a strict 'by the book Whitelighter' chastises Leo for his unprofessionalism when handling the Charmed Ones. Both she and Leo orb out and when they reach the Whitelighter sanctuary, she informs him that she will determine if his feelings for Piper are interfering with his work. Phoebe calls Leo and confesses that she allowed Belthazar/Cole to escape. Leo storms out of the room, but collapses when he feels a witch dying. Natalie orbs in and informs Leo and the girls about Aames' grand plan. He's trying to lure a Whitelighter so that he can kill them with the crossbow and absorb their power. With their powers he can can kill all the Whitelighters, leaving all witches unprotected. Leo feels his emotions are getting in the way and asks Natalie to protect the Charmed Ones. Natalie puts the girls through a witch boot camp and devises a plan, using herself as bait, to draw out Aames. The girls follow the plan, defeat the warlock and get the crossbow, but feel it was too easy. As Natalie is holding the bow it starts to dissolve and Aames appears. He stabs Natalie and orbs out with her. The Charmed Ones call Leo and he tells them he has a plan, but it would involve breaking some rules. Using Natalie's power Aames makes his way to the sanctuary. The girls are waiting for him and take him by surprise. They defeat him and as their reward for saving the sanctuary, the Elders allow Piper and Leo to finally become engaged.