
Revealing mistake: In the scene when Angel, a vampire, runs after the barman towards the end, after the barman has tried to pass on the demon to Kate and Angel stopped him, there is a mirror, and when Angel runs past it, he has a reflection. (00:38:20)
Answer: Due to his epiphany, Angel basically had the 'true darkness' he worked so hard to reattain ripped away from him, like his soul was after sleeping with Buffy.