The sisters were puppets of complex machinery. So fine was their construction that any who laid eyes upon them assumed they were human in every way.
They were the embodiment of man's greatest technological achievements; they walked like humans, ate like humans, laughed like humans. The one thing they could not do, however, was shed tears, for they were not designed that way.
Because the sisters were machines, they felt nothing. Oh, they might mourn as humans did, but they experienced no true sadness, for they did not know what sadness was. Even when their friends perished in tragic accidents and their creator died of disease, they felt nothing. To the sisters, all it meant was that those people no longer existed.
It was a warm spring's day when a lone cat wandered into their home. It was a scrawny, filthy thing, riddled with disease.
"What a bother," the sisters thought as they looked down at the wretched creature.
But they fed it milk, wiped it clean, and kept it warm, and soon the cat was well again. From that day forth, it would linger wherever the sisters were, brushing against their legs when it wanted food.
If it caught a mouse, it would bring it back to boast its prowess. If it wanted love, it would cry out to them in a mewling voice.
It was a cold winter's day when the cat came into their house, let out a feeble squeak, and died. Time and again did the younger sister shake the cat's body. Time and again did the elder sister call out to it. But the cat neither moved nor responded.
In that moment, the sisters felt as though they felt something break deep inside their chests. And from that day forth, they truly felt nothing at all.
The two sisters were a perfect pair of walking mannequins. In no way could you tell they were mechanical. State of the art technology gave them the gift of life, of laughter, of joy, of satisfaction. But, they could not cry. They were never meant to cry.
Being mere dolls, they could not feel. They could be sad, but not feel sadness. Sadness was unknowable to them. Even the death of a loved one. Even as their creator succumbed to disease, they felt nothing. As if their creator had just disappeared from the face of the earth.
One warm spring day, a stray cat approached and greeted them. Covered in scars, riddled with disease and thin as a rail, they took it in, and cared for it. "Ah, what a fuss." Their tender care rejuvenated it, and in time regained it health. From that day on, that cat became a fixture in their daily lives. Every day, it would beg for food, affection, and praise. "Ah, what a fuss."
Winter's cold blew into the house as it staggered in from outside. With a weak meow, the cat's strength slipped, and it fell limply to the floor. The younger shook it again and again. The elder called for it again and again. But in the end, not a single cry, not a single response came. Something in the twins, something deep in their hearts, broke. And from that day on, they felt nothing at all.