Essays / i need to write a horror story for english. i need ideas on starting it off! [7]

the teacher gave me this to start off with but i will get more marks if i make my own up. Im in the top english class and i cant fail this!

I never really liked being alone at night, but I promised my friend I would look after her little sister. I sent her up to bed and I was downstairs watching TV. I was just about to fall asleep when I heared a loud thump outside of the front door. I started to breathe faster and tried to tell myself that it was nothing. Slowly, I walked over to the front door. Another thump- and I jumped back. What the heck could it be? My palms became sweaty as I tried to look through the peep hole. Suddenly, I realised that the door knob was slowly turning...

please help