Theory:

But as soon as the servant stepped out of the room, it struck Bepin Babu that Chuni might remember something about the ’58 trip. There was no harm in asking him.

Bepin Babu hurried down the stairs and into the living room. Chuni was about to leave, but seeing Bepin Babu appear, he turned round hopefully.

Bepin Babu didn’t beat about the bush.

“Listen, Chuni - I want to ask you something. You have a good memory, and you've been seeing me off and on for a long time. Just throw your mind back and tell me - did I go to Ranchi in ’58?”

Chuni said, “’58? It must have been ’58. Or was it ’59?”
Explanation:

Bepin sent his servant to inform Chunilal not to visit him for several weeks. However, as soon as the servant left the room, it struck Bepin Babu that Chuni might be able to recall anything from the $$1958$$ trip since he was Bepin's friend and that he has known Bepin for many years.

Bepin felt no harm in approaching him for help as he was not like Dinesh, who tease him for any of Bepin's mistakes. And so, he rushed into the living room, hurrying down the stairs to meet him. When Chuni was ready to depart, he turned around to meet Bepin Babu hopefully.

As soon as Bepin had seen Chunilal, he didn't speak about anything but directly started his talk about the Ranchi trip. He never helped Chunilal during a crisis but expected help from him. This behaviour of Bepin shows his selfishness and his uncaring attitude towards his friends.

Bepin told him that since Chunilal has an excellent memory and has known Bepin for a long time, he could help him with Bepin's question about the $$1958$$ Ranchi trip. Chunilal, on the other hand, was unsure about the year as it was $$58$$ or $$59$$.

Meaning of difficult words:

 S.No Words Meaning 1. Beat about the bush To talk about something for a long time without getting into the main point
Reference:
National Council of Educational Research and Training (2008). Honeydew. Bepin Choudhury’s Lapse of Memory- Satyajit Ray (pp. 59-69). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.