Theory:

     The ghost was speechless. Marshalling his ghostly wits, he made an attempt to look Vijay Singh scornfully in the eye. “Frankly,” he said, “you don’t appear all that strong to me.”
 
     “Appearances can be deceptive,” Vijay Singh said. “Take your own case. You claim to be Natwar, though actually you are a rascal of a ghost. If you doubt my strength, let me give you a demonstration of it.”
Explanation:
 
The ghost couldn't reply anything. It remained speechless. The ghost somehow gathered its ghostly intelligence and took an attempt to disrespect Vijay Singh's words. It tried to insult him back, stating Vijay Singh doesn't appear to be a strong person for it.
 
The irritated ghost.jpg
The irritated ghost

Vijay Singh had not accepted the ghost' words. He also informed the ghost that one could not estimate a person by looking at his/her outward look as it will cheat without revealing the truth. He gave an example of the ghost itself and informed it that though the ghost claimed itself to be Natwar, he was the idiotic ghost, in reality. Moreover, if the ghost had a doubt on Vijay Singh's power and wanted to check it, Vijay Singh was ready to demonstrate.
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
Marshal
To combine things together
2.
Wit
Intelligence or mental ability
3.
Scornfully
Without respect
4.
Appearance
The way people looks outside
5.
Deceptive
Causing to believe something that is not true
6.
Demonstration
Showing something how it works
Reference:
National Council of Educational Research and Training (2006). A Strange Wrestling Match: Indira David (pp. 43-51). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.