A detective found a diary with ink smeared only on one page. The rest were blank. What might this indicate?

Category: Mystery · Difficulty: hard

Hint: Think about ways messages can be concealed without erasing.

Answer

Invisible ink revealed by heat

Explanation

Invisible ink can be revealed by heat, explaining why only one page showed marks.

This is a hard mystery riddle — a tricky one that takes a little thought. The answer is Invisible ink revealed by heat.

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