If only Griffin had managed to wake up in good time all might have been well. As it was, he did not wake up until the assistants were already arriving next morning. When he saw a couple of them approaching, he panicked and began to run. They naturally gave chase. In the end he was able to escape only by quickly taking off his newly- found clothes. So once more he found himself invisible but naked in the chill January air.
Explanation:

The narrator then says that everything might have ended well if the scientist had woken up early. The statement was made because if the scientist had escaped from the store after stealing the food and trying on the clothes, no one should find him.

Usually, everyone knew that if someone stole something and stayed in that place, the shop owner or assistants would beat them or surrender them to the police. The same thing happened to the scientist. He didn't wake up till the assistants were on their way in the next morning.

When the scientist saw a couple of men approaching him, he panicked and started to run. He had no other go, so he ran from there. Usually, the assistants would chase him if someone stole things from the shop and ran without paying. It happens here, too; the assistants chased him as the scientist started running.

In the end, the scientist could escape from the assistants only by rapidly removing his freshly acquired clothing. Later, he became invisible again and roamed naked in the chill January air.
 
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Griffin became the invisible man
 
Meanings of the difficult words:
 
S.No
Words
Meanings
1
PanicA sudden strong feeling of fear that prevents reasonable thought and action
2
Naked Not covered by clothes
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.