Bowen is an orphaned child in feudal England whose first appearance in this novel is having been bound hands and feet and whipped mercilessly by the monks in a monastery in an excess of bloodlust. He’s realistically of an indeterminate age but no more than about seven years old and the monks are very sadistic. He’s punished repeatedly for any number of minor and inconsequential infractions.

Bowen’s father and mother and sister are dead. His sister was the victim of a brutal rape in which she became pregnant and died shortly after giving birth though she had been returned to her parents’ home in a beaten and catatonic state. His father drowned and his mother burned to death in the family home.

Aaron is a minister in present day Midwest America who takes a short sabbatical after he has a fainting episode while experiencing the marks of the stigmata immediately preceding a sermon that he’s supposed to deliver about Faith Unending, a concept with which he’s struggling himself.

Aaron is continuously having episodes of a fugue like state or altered consciousness in which he’s catapulted back in time. He sees Bowen whipped by the monks and is compelled to take the whipping on himself which in turn leads Bowen to have to leave the monastery where the sadistic monks are calling for his death, citing devil possession.

Lucian is a severely autistic child in the present day who’s found homeless and taken to a mental health center after a fire in an abandoned building in which he’s sleeping. He’s horribly scarred and disfigured and bears a striking resemblance to Bowen and Aaron. He takes a liking of a sort to Aaron, who has eyes of the same amethyst color as his. He also bears a mark on his chest which looks like a brand and is the mark of the Celtic war god Rudianos.

Lucian has a horrible aversion to religious symbols, only speaks Welsh and then only in riddles and in a cold, hateful voice not like a child, “The guardian lives. The gate has been opened. The sins of the father borne upon the son. Vengeance thirsts for blood. The sacrifice must be made.” He also tends to say, “Bless the child, save the child.” All this starts to make sense, along with the rash of fires that follows Lucian wherever he goes when Aaron finds out that Bowen and Lucian are the same person.

Lucian/Bowen’s father awoke an ancient evil whose service he had the strong desire to use for revenge but he didn’t understand that said evil thirsts for living blood and the dead blood of the sister, whom he dug up and tried to offer as payment on a burning pyre, was simply unacceptable. Since he performed a Druid rite under the light of the full moon, each lunar cycle brings with it a fresh hell for Lucian.

Lucian/Bowen is the Guardian of that ancient evil and a perpetual child who has been severely tortured, violated and abused. He’s centuries old though physically still very young and has been left repeatedly to the whims and care of both good families in the past as well as people with sick and obscene appetites, so it was easier to retreat into his own mind where the suffering wasn’t so bad.

Aaron realizes that his compulsion to help Lucian comes from the fact that he’s a direct descendant of Lucian’s nephew, the child of the rape. This is why they bear a stunning resemblance to one another, including the black hair and amethyst eyes. Aaron also realizes that this is why he’s the only one who can help Lucian and he offers his own life to take Lucian’s place as the church they’re in burns to the ground.

When Aaron’s body is found the next morning, Lucian is curled next to him but he’s talking and able to meet peoples’ eyes. He’s judged fairly healthy all things considered and a most unlikely guardian steps forward in the form of a member of Aaron’s congregation, Philip Moran. It’s under the cooperative care of Philip and his sister that Lucian begins to obtain an education and grow up though he always remembers the sacrifice that Aaron made to help him. Lucian begins to live.