A series of knocks were heard but the walls were solid. How was the message transmitted?

Category: Mystery · Difficulty: hard

Hint: Consider alternate ways sound or signals can move through structures.

Answer

Vibrations traveled through the pipes

Explanation

Vibrations conveyed the knocking sounds through connected plumbing, allowing communication without direct contact.

This is a hard mystery riddle — a tricky one that takes a little thought. The answer is Vibrations traveled through the pipes.

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