Angel was the highly successful spin-off from the American television series Buffy the Vampire Slayer. Angel had a darker tone than Buffy, and it at times performed better in the U.S. Nielsen Ratings than its parent series. The series was created by Buffy creator Joss Whedon in collaboration with David Greenwalt, and first aired in October of 1999. Like Buffy, it was produced by Whedon's production company, Mutant Enemy.

The series detailed the ongoing trials of the vampire Angel, who had his human soul restored to him as a punishment after more than a century of murder and torture of innocents, leaving him tormented by guilt and remorse. During the first four seasons of the show, he worked as a private detective in a fictionalized version of Los Angeles, California, where he and a variety of associates worked to "help the helpless" and to restore the faith and "save the souls" of those who had lost their way. Typically, this involved doing battle with evil demons (which, on Angel, are distinguished from well-meaning, neutral and innocent demons) as well as tangling with demonically-allied humans and his own violent nature. The term "demon" when applied to the Angel universe refers to the original or pre-Christian definition of the word, which could just as often be morally value-neutral, as opposed to referring to evil beings exclusively. Although not used, the phrase "extra-dimensional alien" (or something similar) would probably be more appropriate in describing certain characters (Lorne in particular) whose intentions were generally not malevolent.

- From Wikipedia