Kill Switch by Penelope Douglas

But my parents didn’t know Ari was having a party, and
they would definitely hear about it if I called security up.
Walking into the kitchen, I plucked a bottle of water out of
the fridge and uncapped the bottle, taking a drink. I could ask
my sister to come up and take a sweep around the house. It
would piss her off, but she would come if I threatened to tell
Mom and Dad about the party. Heading over to the back door,
I reached for the handle, but as soon as I grabbed it, the door
moved, and I realized it was already open.
My heart skipped a beat, and I instantly reared back. Oh,
shit.
I’d locked it.
“Arion?” I shouted, suddenly alert. “Are you here?”
I pawed for the handle on the outside, finding the key we
hid under a loose brick outside still inserted. It had to be my
sister. Only our family knew where that key was.
“Arion!” I growled, losing my patience. “Knock it off and
answer me!”
She seemed to get off on pranking me this week after the
locker room incident she was probably the mastermind of.
I patted my pockets, realizing I’d left my phone in the
ballroom.
And then I heard it. A few feet away, but I heard it.
Another creak in the floor.
I was paralyzed, frozen in place as my head swam with not
knowing what to do. I tried to swallow but my throat had
closed.
My mouth tried to form the words, but nothing came out.
The floor didn’t move again, and I didn’t even breathe as I
listened.
Someone was there.
I felt it. The presence was heavy, and it was there.