My dad was a big fan of the show "Get Smart." He was in elementary school when he came across a problem--his pens kept disappearing. Another kid was stealing them from him, he was sure of it. My dad thought he knew which one it was, too, after yet another one had gone missing.
"Hey," he said to the kid. "You stole my pen."
"No, I didn't," the kid quickly responded. "It's my pen."
"But I just saw you swipe it off my desk."
"No, you didn't."
"Yes, I did," my dad said. But he did not bother tattling over a single pen.
My dad used the kind of pen that clicks on the top so the ball point pokes out the other end. He knew he could prove the kid had stolen it. He swiped the pen back when the kid wasn't looking.
When he went home he unscrewed the top of the pen and poked a hole through the clicker. Then he set up a safety pin, apparently not so safe, on the inside of the pen so the Pen Theif's thumb would get stabbed to death if he dared try and click it.
And so, the next day he left his pen on the desk for all the world to steal, and left his desk to watch from afar, the Pen Theif take his treasure. To start writing he had to click it, so--
"OW!" cried the Pen Theif. A tiny stream of blood trickled down his thumb. Apparently that was the point on the thumb torturers in medieval times used to crush.
And eventually my dad was sent to the principal's office, for the simple crime of delivering a slice of karma to this pen-burgling criminal.