You are going to write a story that starts with an exciting opening and then "flashbacks" to the events that led up to it.
The main character in the story is Jessica. The opening paragraph (the climax) has been written already, you should complete the story by writing the build-up to the climax and end the story with a cliffhanger.
Part 1 : (The climax)
Jessica was all alone by herself in a completely dark classroom. She was trembling with fear. Before she could make up her mind on what to do, she heard someone trying to open the door.
Part 2 : (The build-up - flashback)
It was about a week ago. Another school day was coming to a close. Everybody was busy packing....
Part 3 : (Revisiting the climax)
Part 4 : (Resolution with a cliffhanger)