Mad Father (fanfic)

A simple family with two adorable daughters, a beautiful mother, and well, a mad father.
I've seen it, just a peek of what father does every night. He and mom would argue over something I don't know. Me and my sister kept it as a secret and pretended nothing happened.
We didn't want our happy life to change. But it was all just a dream until one night...
I had this weird, cold sensation on my back...