Why?

A 15 year old girl was at home alone while her parents were out. When someone called her house when she answered the phone no one was there. They called back 6 times after that. She was wondering what was going on. But when she called to ask her mom the phone got cut off. The electric went out and he phone was dead. Someone was knocking on the door but she didn't open it. She went to the bathroom and sit in the bath tub Incase of a break in. She hears a strange sound coming out of the drain read to see what happens next