Doyle (full name Allen Francis Doyle) had a human mother and Brachen demon father. Doyle had the ability to morph between his human and demonic faces, something which didn’t occur until he was 21 years old. At that time, he was a school teacher and soup-kitchen volunteer, and married to Harriet. Their marriage broke up when neither Doyle nor Harriet could accept his demon-side.

Doyle started receiving mind-splitting visions from the Powers That Be. He had his first vision when Lucas, a fellow Bracken demon, asked for his help against the Scourge, a pureblood sect of militant demons. He turned Lucas away and then saw images in his mind’s eye of Bracken demons getting massacred. Upon seeing their bodies, Doyle confirmed that the visions were real.

Doyle persuaded Angel, who had just arrived in Los Angeles, to carry out his quest for redemption using Doyle’s visions. Together, with the assistance of Cordelia, they formed Angel Investigations, which specialized in supernatural phenomena. Doyle’s visions led Angel to those who were in danger and the two became friends. Doyle had a crush on Cordelia, but was afraid she would reject him upon finding out about his demon background.

When the Scourge returned, Doyle proved himself to be a reluctant hero, by volunteering to die in Angel’s place, sacrificing his life to save his friends, and the city. Before he died, Cordelia learned he was half-demon, telling him it didn’t matter to her. The two exchanged a passionate kiss, and Doyle gave Cordelia his visions.