This is a story that I (jkcclemens) remember from my childhood. I don't know if it's well known.
There was a girl who lived alone with her parents and dog. They were a well-to-do family, and, as a result, they lived in a nice house with a high-end security system. The girl never felt afraid.
One day, the girl's parents told her that they were going out of town and that she would be alone for a day. They figured she was old enough to handle it herself. So, time came for her parents to leave, and they said their goodbyes.
The girl had a normal day. As night came around, she flipped on the TV and watched some shows. She fell asleep on the couch. As it got later, the news came on. She woke up to a story about how a serial killer had escaped and was at large. The newscasters were telling the audience to check that their doors and windows were locked.
The girl went around her house and made sure everything was safe. She checked all the locks and the security system. Everything seemed fine. She lived in a nice neighborhood and had a nice security system, so she wasn't really worried.
She watched some more shows and decided to head to bed. She went upstairs and got changed. She got in bed and reached down to let her dog lick her fingers, like he always did. He loved sleeping under her bed, and she always felt safe when she reached down to pet him and let him lick her fingers.
She rolled over and closed her eyes. Then she heard it. Drip, drip, drip. It was quiet. She assumed that some faucet was barely on and was dripping. Oh well.
However, the girl had a seed of doubt planted in her. She couldn't help but feel a little scared about the loose serial killer. So, she rolled over and pet her dog and felt him lick her fingers. Satisfied, she closed her eyes again.
Drip, drip, drip. The drips were getting louder. She tried to tune them out, but she couldn't. After a few minutes, she got up to go check it out. As she walked down the hall, she came to the bathroom, and the dripping was at its loudest.
She opened the door and looked around. She didn't see what was dripping. Then, she pulled back the shower curtain, and she found the source of the dripping.
Hanging from the showerhead was her dog, dead, blood dripping into the tub. She screamed. She heard her bedroom door open.
Drip, drip, drip.