Theory:

BANG!
I think I'll die with fright
Unless you let me in to-night.
(Shall we let him in, children?)
Ah, now the door is opened wide,
I'm rushing through, I'm safe inside,
The lights are on, it's warm
and grand-
Mistress, let me lick your hand
Before I slip behind the couch.
There I'll hide myself and crouch
In safety till the BANGS are done-
Then to my kennel I will run
And guard you safely all the night
Because you understood my fright.

                                -- by Enid Blyton.
Explanation:
  
Again there was a banging sound. The dog thought he would die because of his intense fear. He asked his master to let him inside the house for the night, and he said he was so scared that he will die that night itself.
 
dog-1550413_1920.jpg
The dog pleaded to let him inside!
  
The master then asked his children, whether they can let the dog in. This line, "(Shall we let him in, children?)" is given in brackets, to indicate that it was spoken by the master, whereas the dog speaks the rest of the poem.
 
The children might have answered "yes" because the door was opened wide immediately. The poor dog ran inside quickly. He felt he was safe inside. There were lights inside the house that made it look magnificent. Outside in the dark, he did not understand what was happening. He became comfortable once he saw the lights and also it was warm. Nights are usually snowy and cold during fireworks night (November month) in the United Kingdom. So the lights provided him with warmth and comfort.
 
He asked his mistress if he could lick her hand. Dogs express happiness, affection and gratitude (thankfulness) by doing such activities. Then he licked her hands and became warm and cosy.
 
dog6.jpg
Once indoors, he felt warm and safe!
 
He went behind the big sofa to hide himself from the sounds and dangers outside. He ducked down in a way to defend and protect himself. He asked his owner that he will stay here in this position in safety until the banging sounds were over. He promised to return to his kennel, after the banging sound. Kennels are small shelter houses for dogs, usually kept outside the house, from where the dogs can keep a watch over the house. He said he would return to his kennel to guard them safely throughout the night because they had understood his fear and let him inside. He was loyal and wanted to repay their kindness by guarding them forever.
 
Meanings of difficult words:
 
No.
Words
Meanings
1
frightsudden, intense feeling of fear
2
rushingmoving hurriedly, in haste
3
coucha high-rise sofa, where more than 2 people can comfortably sit
4
crouchadopt a position where the knees are bent and the upper body is down, typically to defend oneself
5
kennela small shelter for a dog, a dog house
6
doneover, finished
7
mistresslady-owner of a house, hostel, pet animal etc
Reference:
State Council of Educational Research and Training (2019). Term-1 English Standard-8. Firework Night(pp. 141-144). Published by the Tamil Nadu Textbook and Educational Services Corporation.