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Vulferym looked down his nose at the bag he was handed. He scoffed, and took it, then immediately dropped it back to the floor, and ignored it. He looked around. Another door had appeared, with a box on each side of it. He walked over and opened the door. There was nothing on the other side but a wall, not two inches from the doorframe. Vulferym scoffed again, and turned to inspect the boxes. One said “eat me”, the other said “don’t eat me”. He opened the “eat me” box, and saw an array of sweets inside. The “don’t eat me” box had the same.

“Looks like a puzzle.” A voice from behind him spoke up. The one called Virtus.

Vulferym frowned. This castle made no sense. Metal dragons and doors that led to nowhere, boxes of sweets that were supposed to be puzzles…

But, lucky for them all, I’ve seen this kind of thing before, thought Vulferym. It’s just like what Father used to do with Favian and me. Puzzles that we’d have to solve using logic and reasoning.

“Of course it is,” said Vulferym. “My uncle loves puzzles. The sweets in each of the boxes are going to make something different appear on the other side of the door. What appears depends on which box is eaten. Either something good, or something quite undesirable. We just have to figure out which box is which.”

Vulferym looked around. They were all watching him, and a couple were even nodding reluctantly, as if they didn’t want to admit that what he was saying made perfect sense. Good, good. He went on,

“But this is the same puzzle as one my uncle gave me as a child many years ago. He must have known I’d remember.”

He spoke slower now, as he presented his logic. “The bad sweets are obviously not in the box that says “don’t eat me”, because that would be much too obvious. But he would know we would think that way, so he would actually put them in the “don’t eat me” box. But he would also have to assume we would reason that part out, so he wouldn’t put them in that box after all. Which means they’re actually in the “eat me” box.”

He took a breath, and continued. “But, he has to assume that, if we thought it through this far, we would reason this one out as well. There’s no reason for us to stop here. He knows that. So he wouldn’t put the bad sweets in the “eat me” box, because he would know we would think this far.”

Virtus spoke again. “So, the bad ones are in the “don’t eat me” box?”

Vulferym smiled. “No. They’re in the “eat me” box.”

“But you just said-”

“I know. But think about it. We’ve reasoned out that they’re actually in the “don’t eat me” box. We’re confident of that. But wouldn’t he know that? So he doubles back on himself now, and actually does put them in the “eat me” box. So we need to eat the sweets in the “don’t eat me” box. Another way I know this to be the case is this: Suppose we didn’t reason it this far. Suppose we only got past the “it’s too obvious for the bad ones to be in the “don’t eat me” box, so obviously they’re in the “eat me” box”. We would eat the sweets in the “eat me” box, because we think we out-reasoned him. But we didn’t. The bad ones were in the “eat me” box all along.”

He looked around, and smiled. This time, it was a real smile. He realized that with a jolt of surprise. He actually was happy.

“We need to eat the sweets in the “don’t eat me” box. Make sense?” he asked.