Allen Francis Doyle is a fictional character created by Joss Whedon for the cult television series, Angel. The character was portrayed by the late Glenn Quinn. Doyle was born to a human mother and a Brachen demon father.
Doyle never knew his father or anyone on that side of his family, and his own demonic genes didn't physically manifest themselves until he was 21 years old. At that time, Doyle was a third grade teacher and a soup kitchen volunteer married to a lovely woman named Harriet, the love of his life. He didn't take the news of his demonic heritage very well: in spite of Harriet's acceptance of his other side, his marriage ultimately disintegrated.
Doyle hid behind the flimsy veneer of a ne'er-do-well hustler and con artist, seemingly more interested in where his next drink was coming from than helping others. Later, he was approached by a fellow Brachen demon, Lucas, who told Doyle the Scourge, a militant group of pure blood demons, was after all half-breeds and begged for Doyle's help. Doyle turned Lucas away, believing this wasn't his problem.
Soon after he received a vision, which he described as "splittin' migraines that come with pictures," in the throes of which he thought he was having a stroke. The vision showed him a group of massacred Brachen demons. Doyle searched the city to find out if what he had seen was real--it was.
These visions, which come from The Powers That Be, are what led Doyle to Angel. As Doyle says, "We all got something to atone for," and therefore the two join forces to fight evil in Los Angeles. Once Cordelia Chase joins the team, Angel Investigations is officially formed.