 After being marked by the vampire Kurt Barlow, and therefore forced out of his church, Father Callahan spends time volunteering in a homeless shelter.Callahan made it a goal to get even with the vampires for what they did to him and his friend, who contracted HIV after being bitten by a vampire.He is aided in this by his ability to spot the vampires; since Jerusalem's Lot (and the forced ingestion of some of the vampire Barlow's blood) he has been able to recognize vampires on sight.