"Is this what it looked like?" Fr. Marcus as he showed Catelyn and Mary Margaret an etching from one of the library's books.
"That was it," answered Catelyn. With those X-ed out eyes, who could mistake it?
Fr. Marcus nodded and shut the book. He let out a long and slow sigh.
It was Mary Margaret who finally spoke up. "Father, what was it?"
"It was a Harbinger, Mary Margaret."
"A what?"
"A priest."
"Well, he wasn't wearing the clerical collar," pointed out Catelyn. "And I don't think it was Episcopalian."
"A high priest of the First Evil," clarified Fr. Marcus. "The most absolute of evils, older than both men and demons."
"And why was this thing in our bedroom?"
Fr. Marcus did not answer for a while. "You both know what a Slayer is?" he asked.
Catelyn nodded. "Into each generation, a Slayer is born: one girl in all the world, a Chosen One, one born with the strength and skill to hunt the vampires, to stop the spread of their evil. She alone will stand against the vampires, the demons and the forces of darkness. She is the Slayer, et cetera et cetera and so on and so on. She's a girl in California."
Mary Margaret added, "I heard there's two Slayers. One in Sunnydale, but the other one is in jail."
Fr. Marcus nodded. "That's correct, Mary Margaret. But in every generation, there are hundreds, perhaps thousands, of girls who could have been the Slayer. The Council of Watchers, who guides the Slayers, never knows which girl will be activated as Slayer when the past Slayer dies. So they try and find as many of these potential Slayers as they can and train them, preparing them for the day when they may be Slayers. Sometimes, however, the potential Slayers fall under the jurisdiction of some institution which the Council trusts, and in those cases the Watchers do not interfere. St. Clare's is one such institution."
Catelyn looked at Fr. Marcus wide-eyed. "Then you mean...."
"Yes, Catelyn," Fr. Marcus answered. "Mary Margaret is a potential Vampire Slayer."

A/N: Thanks to karabair for asking if Catelyn (who appears in my "Windows of My Soul") was a Slayer and prompting this story.