Karyn picked up a chair. Her best friend had just tried to rape her. She didn't know if it was some effect of the stone, or if he had been hiding his tendencies from her all these years, or if he accidentally wished himself evil, or if he was even himself and not possessed. Or if he was himself and had just snapped. But she knew she had to stop it.
She raised the chair and swung it at Jon's head.
"That won't work," said Jon. Karyn paused. "The moment you touch me with that you'll be in a brothel on the other side of the world."
Then Karyn swung the chair. Jon didn't even bother to dodge it. He knew that he would be safe. It came down, down... and hit Jon square in the center of the head. He collapsed to the floor. He might be out for days, if she hadn't killed him outright--concussions aren't as easy to survive in reality as they are in the movies.
She had figured it out Jon's mistake the moment he explained his wish, but there was no way she was going to tell him. The stone couldn't transport her to a brothel on the other side of the world--that would be outside its range limit.
Karyn took the stone from Jon's limp hand and ran off trying to find help. She couldn't use the stone herself, so who could she trust? Who could she even convince?