Father Donald Callahan Timeline & Summary

Father Callahan serves as parish priest in 'Salem's Lot.
Matt Burke calls Callahan and convinces him there are vampires in the Lot. He then convinces Callahan that the Lot is infested with giraffes. Okay, that doesn't happen.
Callahan goes with the other vampire hunters to the Marsten House. He blasts the door open using his cross, much to his own surprise.
After Ben stakes Susan, Callahan blesses the house and seals it with the Host, closing it to Barlow. Superpriest!
Mark and Callahan go to the Petries' house to warn them that Barlow threatened them.
Callahan argues with Henry Petrie about the existence of vampires; then Barlow shows up and kills Hank and his wife.
Callahan holds Barlow at bay with his cross for a bit, and Mark escapes. This is the high point for superpriest; all downhill from here.
Callahan loses faith. Instead of turning him into a vampire, Barlow forces Callahan to drink his blood. That's nasty.
This marks Callahan; when he tries to enter a Church, he is thrown back and his hand is burned.
Callahan, defeated and consumed with self-loathing, gets a bus out of town for New York.