Theory:

     They fell into each other’s arms, so surprised and relieved that all they could do was laugh and giggle and repeat each other’s names.

     Then Usha said, ‘I thought you were ghosts.’

     ‘We thought you were a ghost!’ said Suresh.

     ‘Come back under the roof,’ said Usha.

     They huddled together in the corner chattering excitedly.

     ‘When it grew dark, we came looking for you,’ said Binya. ‘And then the storm broke.’
 
     ‘Shall we run back together?’ asked Usha. ‘I don’t want to stay here any longer.’

     ‘We’ll have to wait,’ said Binya. ‘The path has fallen away at one place. It won’t be safe in the dark, in all this rain.’

     ‘Then we may have to wait till morning,’ said Suresh. ‘And I’m feeling hungry!’

     The wind and rain continued, and so did the thunder and lightning, but they were not afraid now. They gave each other warmth and confidence. Even the ruins did not seem so forbidding.
Explanation:
 
All three children fell on each other, and they were all so glad, so they all just laughed at each other and repeated their names.

Usha said that she thought they were ghosts.

And Suresh replied that they thought she was a ghost.

Usha asked them to come under the roof.

They hugged each other and started talking.

Binya said that they both came looking for Usha as it grew dark, and suddenly the storm started.
 
Usha asked if all the three of them run back together, as she didn't feel like staying there anymore.

Binya said that they would have to wait as the road has fallen away in one place, so it will not be safe for them to go in this night that too when it's raining.

Suresh was feeling hungry and asked if they have to wait till morning to go back to their village.

The wind, rain, thunder, and lightning continued, but now they were feeling better, they were not scared. The children had faith in each other, and the ruins were not scary anymore.
 
Meanings of difficult words:
 
Numbers
Word
Meanings
1.
Relieved
Glad.
2.
Giggle Snigger.
3.
Chattering Chitter-chatter.
Reference:
State Council of Educational Research and Training (2019). Term-1 English Standard-7. The Wind on Haunted Hill by Ruskin Bond  (pp. 25-34). Published by the Tamil Nadu Textbook and Educational Services Corporation.