“What logical puzzle?” said the Archchancellor. “Well,” said Ponder, gratified at the attention, “it appears that there was this man, right, who had to choose between going through two doors, apparently, and the guard on one door always told the truth and the guard on the other door always told a lie, and the thing was, behind one door was certain death, and behind the other door was freedom, and he didn't know which guard was which, and he could only ask them one question and so: what did he ask?”
The coach bounced over a pothole. The Librarian turned over in his sleep.
“Sounds like Psychotic Lord Hargon of Quirm to me,” said Ridcully, after a while.
“That's right,” said Casanunda. “He was a devil for jokes like that. How many students can you get in an Iron Maiden, that kind of thing.”
“So this was at his place, then, was it?” said Ridcully.
“What? I don't know,” said Ponder.
“Why not? You seem to know all about it.”
“I don't think it was anywhere. It's a puzzle.”
“Hang on,” said Casanunda, “I think I've worked it out. One question, right?”
“Yes,” said Ponder, relieved.
“And he can ask either guard?”
“Yes.”
“Oh, right. Well, in that case he goes up to the smallest guard and says, Tell me which is the door to freedom if you don't want to see the colour of your kidneys and incidentally I'm walking through it behind you, so if you're trying for the Mr. Clever Award just remember who's going through it first.'”
“No, no, no!”
“Sounds logical to me,” said Ridcully “Very good thinking.”
“But you haven't got a weapon!”
“Yes I have. I wrested it from the guard while he was considering the question,” said Casanunda.
“Clever,” said Ridcully. “Now that, Mr. Stibbons, is logical thought. You could learn a lot from this man-”
“-dwarf-”
“-sorry, dwarf. He doesn't go on about parasite universes all the time.”
“Parallel!” snapped Ponder, who had developed a very strong suspicion that Ridcully was getting it wrong on purpose.
“Which ones are the parasite ones, then?”
“There aren't any! I mean, there aren't any, Archchancellor.[15] Parallel universes, I said. Universes where things didn't happen like-” He hesitated. “Well, you know that girl?”
“What girl?”
“The girl you wanted to marry?”
“How'd you know that?”
“You were talking about her just after lunch.”
“Was I? More fool me. Well, what about her?”
“Well. . . in a way, you did marry her,” said Ponder.
Ridcully shook his head. “Nope. Pretty certain I didn't. You remember that sort of thing.”