In the shadows under your bed, a monster gnaws at the edge of reality. Do you hear the munching sound?
It is the anti-mouse.
Every mouse killed by poison could become one. Most mice are quite simple creatures: they eat because they're hungry. But a very few are bad mice: they eat because they can.
You see, it is only with cleverness that the capacity for good or evil exists. Dumb beasts destroy because they don't know any better, but when the clever ones destroy something, you can be sure they do it with intent. And sometimes that intent lives on after them.
A clever mouse dying of a poison trap dies slowly and painfully, and he has time to think. He thinks about how unfair it is that he should die while so many others live. He thinks about how much he hates you for killing him - oh, yes, he knows. He is clever after all.
And when a mouse is clever, he thinks about eating the whole world.
After the mouse has died, and you have carried the small furry body to the trash heap, the cleverness stays behind, and with it, the ill-intent, and it flows together and forms a mouse-shaped hole in the universe. Thus is born the anti-mouse.
See how he's nibbled away the night just there, unraveling the corner of that pleasant dream you were having? They really will eat anything.
Given time - and what else do dead things have, really, but time? - they will eat everything.
Oh, you cannot stop the anti-mouse. Not you, and not I. That takes cats. But not just any cat will do.
All cats are born to hunt. Not only mice, but anything they can catch. It's in their nature, and in their form - the shape of their teeth, the spring in their legs, their lithe and twisty bodies, these are the hallmarks of a predator. Every cat is a little lion, and every cat knows it, until we convince them otherwise.
It is a cruel thing we do, to keep them as pets, as cruel as any cramped and confining cage, no matter how many cat treats we offer, no matter how many scratching posts we provide. The wildness in them grows fat and content and they forget what it is exactly lions are for.
Sometimes we can make it worth their loss, but only a very great love can do this. When a cat knows that you would move the moon and stars for them, it makes a minor inconvenience like the loss of their identity seem quite tolerable, for a while at least. All cats think they have nothing but time, you understand. That is why they sleep all day, and laze about, and move with such unhurried grace. And a cat who is loved - who is petted and praised, whose owners tell him sincerely and often how perfect he is, how beautiful he is, and what a clever boy he is (Ah, do you see?) - well, such a cat will think, "I shall enjoy this attention for now. I will have time later for the whole predatory thing."
But only the dead have that kind of time.
And when such a cat dies, a new thing emerges from the cat-shaped hole they leave in your heart: a little lion with all the time in the world, who finally remembers what he was born to do.