Perhaps?

Coming up with a few more opening ideas, getting a little collection before I decide which one to use in my short story. 

1. -----------------------
 They turned back and ran down the steps. They knew what they had seen. They weren't even meant to be there; just following a friend into an apartment. She'd been sneaking around for three weeks - they had to see what she was up to, if anything. But, what they saw enlightened them to the fact that, she was up to something, something big. Something that would change their lives in a short space of time, they were now a part of it.

2. -----------------------
She stared into the darkness. Sophie was fascinated by it; the mystery in the abyss - how it could swallow any object or thing. She was never one to ask for the nightlight to be kept lit, Sophie found peace in the dark. Never scared of closet monsters, or the ones that hid under your bed, the ones that watched you whilst you slept. She was brave, braver than most girls her age - she had to be, for the things she had been through were darker than most.

3. Try the use of first person.       ------------------------
Everyone in the office turned and stared. That was the second time this week that my boss had brought me into his office to shout at me. For one, I had done nothing wrong - my work was completed on time, I was way ahead of schedule, yet, my co-worker seemed to like putting me into the shit. Literally, on one occasion. He likes to play practical jokes and when I turn to fight back - that is when my boss walks into the room, finding me in the act. But, today I have had enough. After the prank this morning, there was no way things were going to stay the same.