From Inside the Grey House:
“I’m a Slayer. I hear the Angels and I kill Hellspawn for God at His request. I wasn’t able to hear you because we’re only alerted to the comings and goings of Hellspawn. I have also sworn to protect humans from the truth in the darkness. Though not all of my brethren care for the human race, I do. I recognize that we all begin as humans and are tainted or blessed as needed. Because of my self-appointed role, I’m able to tell when a human is nearby, to ensure that I don’t expose them to the truth. You, you are neither fully human nor tainted by Hellspawn. I would accuse you of being nothing, but that wouldn’t be the truth. You are the One Walking the Edge, and I’m not able to predict where you will fall.”
“And you’re telling me this, because?”
“You would have figured it out on your own eventually.”
“What does this all mean? Can the other Slayers sense me?”
Cat Stark 