This is kind of story based and each one of us adds on to it. We are in a situation based on the last post and create what happens next.
example:
1st person to post the situation - I am tied to a chair in a dark basement.
the action - I cut my hands and legs free of the ropes and run through a door.

2nd person to post the situation - Running down a long dark hallway,
the action - I run into a dead man hanging from the ceiling.

3rd person to post the situation - Being stopped by a hanging dead man,
the action - I scream for help.

4th person post the situation - I am screaming for help,
the action - many hanging dead men come back to life.

You can follow that story lead. Be as creative as you can be but remember this is horror story based and we want to live.