Theory:

     TIMOTHY, the tiger-cub, was discovered by Grandfather in the Terai jungle near Dehra.
 
     One day, when Grandfather was strolling down the forest path at some distance from the rest of the party, he discovered a little tiger about eighteen inches long, hiding among the intricate roots of a banyan tree. Grandfather picked him up, and brought him home. He had the distinction of being the only member of the party to have bagged any game, dead or alive.
 
     At first the tiger-cub, who was named Timothy by Grandmother, was brought up entirely on milk given to him in a feeding-bottle by our cook, Mahmoud. But the milk proved too rich for him, and he was put on a diet of raw mutton and cod-liver oil, to be followed later by a more tempting diet of pigeons and rabbits.
 
     Timothy was provided with two companions—Toto, the monkey, who was bold enough to pull the young tiger by the tail, and then climb up the curtains if Timothy lost his temper; and a small mongrel puppy, found on the road by Grandfather.
 
     At first Timothy appeared to be quite afraid of the puppy, and darted back with a spring if it came too near. He would make absurd dashes at it with his large forepaws, and then retreat to a ridiculously safe distance. Finally, he allowed the puppy to crawl on his back and rest there!
Explanation:
 
The story talks about the author's grandfather, who discovered a tiger cub, in the Terai jungle near Dehra. The town of Dehra was initially a British camp. It is now located in Himachal Pradesh, India. In the nineties, it was very common for men to form hunting groups and trap animals like rabbits or deer.
 
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An aerial view of Dehra
 
The grandfather had similarly gone to a hunting trip into the forest, with his other group members. He had fallen behind the rest of the group and was wandering alone, observing the surrounding areas of the forest, when he first came across the tiger cub. He was around eighteen inches long, meaning it was very young, probably a newborn that was abandoned in the middle of the forest. He was seen hiding behind the deeply entangled roots of a banyan tree. This shows that he was scared of the outer world and was hiding from the completely new environment. The innocence and pathetic situation of the tiger cub forced the grandfather to take him into his care. In fact, the only person who could lay his hands on any animal on the day of the hunting trip was grandfather, since the others did not get any animal, be it dead or alive. The author emphasizes on the fact that grandfather who had gone to hunt an animal and bring it dead, had managed to bring a wild animal like tiger alive.
 
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Tiger cub
 
The tiger cub was named Timothy by grandmother and since he was a young cub,  he was fed milk. The cook Mahmoud fed the tiger in a feeding bottle in a similar fashion to feeding infants and toddlers. But the milk was rich in nutrients for him. He could not take it as he was very young. Therefore he was given meat which is the usual food that a wild animal takes. He was given raw mutton and cod-liver oil, which is a supplement made of fish oil. As he grew up, he was given a lavish meal that included heavy meat like rabbits and pigeons.
 
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Tiger being fed milk in a feeding bottle
 
The tiger had two companions - Toto the monkey and a small mongrel puppy. The monkey was naughty and bold. When other animals would be sacred to near a tiger, the monkey very easily pulled the tail of the tiger and played with it. When the tiger got angry, the monkey easily climbed up the curtains so that the tiger could not reach him. The mongrel puppy was brought home by grandfather in a similar fashion to the tiger. He was found on the road. Initially, the tiger who is much mightier than the puppy, is scared of the tiny puppy that he takes two steps back when it approaches him. He uses his paws for self-defence as he thinks that the puppy is dangerous. But soon there is a turn of events as they become friends to an extent where the puppy is allowed to crawl on his back and rest there.
 
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Monkey playing with tiger
  
Meaning of difficult words:
 
SI.no
Words
Meaning 
1
JungleThick forest
2
Stroll A small walk 
3
Intricate Small things put together in a complex way
4
Bag a gameGetting a prize or reward; mostly used as a term to denote the trapped animals that one hunts 
5
Diet A plan for eating food 
6
Tempting
Making one want for it or like it 
7
DartedTo move quickly
8
AbsurdSilly; that which does not make sense
9
RidiculousUnreasonable
Reference:
National Council of Educational Research and Training (2007). A Tiger in the House - Ruskin Bond (pp. 58- 65). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.