Brilliant scientist though he was, Griffin was rather a lawless person. His landlord disliked him and tried to eject him. In revenge Griffin set fire to the house. To get away without being seen he had to remove his clothes. Thus it was that he became a homeless wanderer, without clothes, without money, and quite invisible — until he happened to step in some mud, and left footprints as he walked!
Explanation:
 
The narrator then says that even though Griffin was a brilliant scientist, he was a lawless man. The narrator then explains to his readers why he said so. He narrated the scientist's past story. He says that the scientist's landlord (the owner of the land or house) hated him. It might be because he knew that the scientist was trying some horrendous experiments in his house. As his landlord disliked him, he tried to send him away. As a result, the scientist set fire to the landlord's house.
shutterstock_358731056 (1).jpg
Griffin set fire to the landlord's house
 
As we know that if someone commits a crime, they should be arrested by the police. Likewise, the scientist Griffin knows about the crime he committed. Griffin tried to be invisible to escape from the people and the police. We learnt that he had consumed a rare drug to become invisible in the earlier paragraphs. After setting fire to the landlord's house, he becomes invisible by removing his clothes. It shows that he had already consumed the drug. When he removed his dress, he became invisible.

Finally, the scientist became a homeless man. He wandered without money and clothes. Also, the main thing was that he wandered invisibly. His presence was only felt after he stepped in some mud, and his footprints could be seen as he walked.
 
Meanings of the difficult words:
 
S.No
Words
Meanings
1
Lawless manDoing activities against the law or doing illegal activities
2
Landlord A man who rents out the land, a building, or accommodation
3
DislikeTo not like someone or something
4
Eject To force someone to leave a particular place
5
Homeless Without a home
6
WandererSomeone who often travels from place to place, especially without any clear aim or purpose
Reference:
National Council of Educational Research and Training (2007). Footprints without Feet - H.G. Wells(pp. 26-31). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.