Having just witnessed the brutal murder of his mother at the hands of his own father, 6 year old Jericho Coleman finds himself moments away from his own extinction. His only chance at survival comes from a mysterious devil, who offers to save Jericho in exchange for refuge within the boy's mind. So begins a lifelong union between man and demon, one which will determine the very fate of Jericho's soul. He does not encounter the demon who rescued him, Mavado, again until many years later; Mavado begins to appear in his dreams, and in spite of their opposing natures the two slowly develop a friendship. At the age of eighteen, Jericho's world is instantly transformed. He finds his union with the demon is far from unique when he is confronted with the reality that the possessed, both good and evil, live among us. Those possessed by demonic spirits are hunted by the Watchers; holy beings who have united with a living host to battle the demonic in preparation for Armageddon. In spite of his unholy union, Jericho manages to negotiate a shaky alliance with the Watchers. Acting as a freelance demon hunter, he attempts to use the evil within him against its own kind, but instead finds himself surrounded by enemies on all sides. In a world filled with monsters, Jericho is confronted with a difficult question: do you trust the devil you don't know, or the one who lurks within?