Deaton and Dr. Valak in “Unfinished Business”

I was hoping we could talk. My name is Dr. Alan Deaton.

Oh, I know your specialty, Dr. Deaton, and I know it's not cats and dogs.

I'm here because of what you know about South American mythology.

No. You want to know about Kate Argent. You want to know about La Loba, the Bone Woman.

I need to know what she did to Derek Hale. And, if he's dying.

Why?

Because of a promise I made to a woman I loved.