Scared of anyone sleepwalking

by Sara

My 6 year old sister sleepwalks. She once walked straight into my room and sat on top of me. Ever since, I've been scared of anyone sleepwalking. I've even gone as far as to locking myself into my room so as to keep her out. Every time my sister gets up and starts walking, I begin to sweat and by breathing goes heavy.
Why am I scared? I've never been so scared of anything like this in my whole life.