John Constantine is an exorcist, demonologist and petty dabbler of the dark arts. Born in Liverpool, Constantine is raised by an abusive father who blamed him for the death of his mother Mary Anne in childbirth. Later learning that he is descended from the legendary Laughing Magicians, which explained his ability to perceive the true nature of supernatural beings at an early age, John grew up highly cynical and cunning with an interest in the dark arts. In his teenage years, he was introduced into the occult and became a respected legend among the dabblers of magic. But John's inability to save a young girl named Astra from a demon he summoned to save her from a weaker one had damned his soul.

While he intended to retire at Ravenscar Psychiatric Hospital, Constantine finds himself dealing with the converging supernatural threats that constantly break through to his world, hoping of redeeming his soul from eternal torment by stopping the apocalypse from occurring.