The Curse

A curse. No one knew when it had started, but it had. It took over an innocent mind, enslaving it and making it murder anyone the curse wanted to kill. When that person would die, the curse would take on someone else. The victim would slowly forget their humanity to a point where they would forget their own name, and be more than willing to kill their family.
How do I know? My twin sister was one of these victims. She died because of it. And now, I truly felt that I was next.