Deep in Siberia, on a barren moraine at the foot of a boney ridge, stood a long-forgotten prison. The mortar had crumbled from between the stones, and the walls and turrets had begun to fall apart, returning into the rocky wasteland they had come from so many years before. No one ever left the dismal place, and no one new ever arrived.

Inside the cells, the same prisoners shuffled about, day in and day out. There were never any new faces staring over their cold meals, never any new feet shambling in chains through the courtyard. Nothing ever changed.

Because there were no new visitors ever, the prisoners had no new jokes to tell. They told the same ones over and over for decades. The inmates knew each joke so well they didn’t even bother with the ordeal of telling the entire thing; they simply assigned every joke its own number. So when one prisoner wanted to break the monotony of the day, he’d yell through his barred door into the dungeon corridor, “Joke number 54!” The other prisoners would mumble and grumble, “Not that joke again,” or “We’ve heard that joke so many times it isn’t even funny anymore.”

Later another prisoner might yell out, “Joke number 112!” Again the prisoners would mumble and grumble, “Not again. It is such a stupid and boring joke,” or “It might be funny if we haven’t heard it a thousand times already.”

One day a prisoner, after walking to-and-fro in his cell all morning, decided it was time for a joke. He stepped to the bars of his door and shouted out, “Joke number 87!”

The usual moans and groans responded. “Give us a break,” said one.

“That’s not funny anymore,” said another. “We’ve heard it so many times.”

But somewhere at the far end of the corridor, someone started laughing. The other prisoners were baffled. No one ever laughed at these old jokes. They called out to him, “Hey! Why are you laughing?”

The amused prisoner could barely step to the bars because of his laughter. When he finally caught his breath, he said, “I haven’t heard that joke before.”