The rain pounded against the windows like it was trying to break into the house, hard and relentless. Thunder rumbled deep in the sky, shaking the whole place a bit, making the lights flicker now and then. It was one of those wild stormy nights where everything outside looked blurry and dark, except for the quick flashes of lightning that lit up the yard like daytime for a split second. My sister, Emily, had called it a night early because she had to be up for work at dawn. 

She was beat from the day, and with the weather turning nasty, she didn't want to drive home. Her best friend,...