Angel returns from Sunnydale, having successfully helped keep Buffy alive. He thinks she has no idea he was even in town. Until Buffy appears at his office, none too pleased. Angel tries to explain that he thought it was easier for both of them if they didn't interact while he was there. Buffy chalks it up to another case of Angel thinking she can't handle things. Their conversation is interrupted when a demon bursts in through the window. Angel and Buffy battle with him. Angel wounds him just before he jumps out h window.
Buffy and Angel track him through the sewers. They have another "heartbreaking sewer talk". Buffy decides it would be better if they split up to look for the demon. She heads up to the surface to look for it while Angel continues his search down below. He meets up with the demon and they fight. Angel is cut during the skirmish. He slays the demon but is infected by its blood when it seeps into his wound. Suddenly his heart begins to beat. He's alive.
Angel returns to the office and reveals his newfound humanity to Doyle and Cordy just before he gets the munchies. He sends Cordy to find Buffy while he and Doyle try to figure out what happened. They discover it was a Morra demon (hired assassins) but still have no answers. Doyle and Angel go to the Oracles to ask if The Powers That Be had anything to do with the change in his status. The Oracles inform him that The Powers had nothing to do with it. He's no longer a warrior. He's a mortal man. Permanently. Angel immediately goes to find Buffy. He walks to her in the sunlight and kisses her.
At first, they decide to be rational and mature and take things slowly. Moments later they are in each other's arms, making up for lost time. They have a perfect evening together. Until Doyle has a new vision. The Morra demon has regenerated itself and is more powerful than before. Angel and Doyle leave to kill it. Buffy awakes and finds Angel gone. Cordy slips and tells her where Angel went. She takes off after him. The newly mortal Angel isn't doing well against the demon. Buffy shows up and destroys it. But not before the demon announces that there are soldiers of darkness approaching to bring on the end of days. Angel goes to see the Oracles again to ask if he was telling the truth. The Oracles reveal that Buffy will die. Angel offers to give up his humanity. He feels he can be of more help to Buffy as a vampire. They agree to turn back time. The last 24 hours will have never happened. Only Angel will remember what events have transpired. He returns to Buffy and tells her what he's done. They share a heartbreaking final moment before time is turned back. This time when the Morra demon bursts in on Buffy and Angel's conversation, he destroys it immediately. And Buffy walks out of his office and his life.