One evening, the noise returns and is so loud and frightening she bolts the front door, leaving her dog barking hysterically on the front porch, until suddenly... silence. The next morning she inspects the scene only to find her dog is missing, the porch splattered with blood.
"Nobody ever found out."
Read the complete text of the story above. While "The Whistle" leaves it a mystery, I have my own theory. The dog could very well have been the victim of a shadmock.
What is shadmock? To explain, I'll first need to brief you on the confusing geneology of monsters. Luckily there's a visual aid for that.
You see, the three primary monsters at the top of the family tree are the vampire, the werewolf and the ghoul. When a vampire and werewolf breed, the offspring is called a werevamp. A werewolf and ghoul produce a weregoo, while a vampire and ghoul produce a vamgoo.
A weregoo and werevamp make a shaddie, weregoo and vamgoo a maddie, and werevamp and vamgoo, a raddie. Now any combination of shaddies, maddies and raddies results in a mock (a polite term for mongrel).
And should a mock mate with any of the other hybrids... they produce a shadmock, lowest on the monster geneological hierarchy.
Shadmocks do not bite or tear at their victims... they only WHISTLE. But their whistle is very deadly. There was one particular shadmock who lived at a remote English castle, so remote that his only friends were the pigeons.
...and before he could do anything about it, the cat had a mouthful of pigeon.
...and in short order, the cat turned into, well... this.
You don't even want to know what happened to the woman he was wooing after she tried to run out on him and he had to whistle for her to come back home.
The story of the shadmock comes from the 1980 cult classic The Monster Club (here's a rendering of the unfortunate cat incident as it appeared in the comic book adaptation of the story)