Question

Q1. What was the mystery behind
the muddy footprints? How did the 2 boys react to that?​

Answer 1

Explanation:

The two boys followed muddy footprints being made fresh without seeing anybody making the prints, which was a 'mystery' for them. The explanation was that the bewildered boys had been following a scientist who had just discovered how to make the human body transparent, and thus invisible, by swallowing certain drugs.