How did the invisible man first become visible?

Griffin was a scientist. He had carried out experiments to make a drug that could make human body invisible. He consumed that rare drug and his body became invisible as a sheet of glass. He was completely invisible until he happened to step in some mud, which caused him to leave footprints as he walked. His footprints were seen by two boys, who followed him as long as the prints were visible. On getting rid of them, he went into a big London. He lost the boys easily. It was winter and he put on some warm clothes from the store after it got closed and got dressed by putting on shoes, an overcoat and a wide-brimmed hat. This made him visible to the people who came to work at the store the next day.

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