Theory:

     John had many stories to tell of dogs and horses, and the wonderful ways they had saved the lives of people. He thought many people did not take very good care of their animals or make friends with them as they should do.

     At last, we got back to Master’s house. We saw that all the lights were on. As we came up to the door, Mistress ran out to greet Master.

     “Are you safe, my dear? Oh! I have been so worried about you. Did you have an accident?”

     “No, my dear, but if Black Beauty had not been wiser than we were, all three of us would have been drowned at the wooden bridge.”

     They went into the house and I heard no more. John took me to the stable. Oh! What a good supper he gave me that night. And then a really thick bed of straw. I was grateful for everything for I was tired.
Explanation:
  
John also had experiences to share about instincts of dogs and horses. He knew the stories of the lovely ways those animals had saved the lives of people. He felt many of them did not treat animals properly. They did not care for them or befriend them.
 
Finally, they reached the master's house. The lights were still on in the house.
 
house lights.jpg
All the lights were on at the master's house!
 
As the cart pulled up near the door, the master's wife came running to the door, to see the master. She asked him if he was safe and told that she had been worried about him. Since the storm was bad, the Mistress was scared whether they would return home safely that night. She also asked if they had met with an accident since they were late.
 
The master said they did not meet with an accident, but if Black Beauty had not been wiser than them, then all of three of them would have drowned at the wooden bridge. They went into the house, and the horse could not hear anymore of the conversation. John took the horse to his stable.
 
John in stable.jpg
John took the horse to the stable and gave him a nice supper!
 
He gave him a nice dinner that night and a thick bed of straw for him to rest for the night. The horse was thankful for everything, but he was also very tired after pulling through the storm.
 
Meanings of difficult words:
  
No.
Words
Meanings
1
supperan evening meal, typically a light or informal one.
2
gratefulthankful
Reference:
State Council of Educational Research and Training (2019). Term-1 English Standard-8. When Instinct Works - Anna Sewell(pp. 145-151). Published by the Tamil Nadu Textbook and Educational Services Corporation.