Theory:

     Just before lunch Bepin Babu decided to ring up Dinesh Mukerji. It was better to settle the question over the phone; at least the embarrassment on his face wouldn’t show.
 
     Two-Three-Five-Six-One-Six. Bepin Babu dialled the number.
 
     “Hallo.”

     “Is that Dinesh? This is Bepin here.”

     “Well, well — what’s the news?”

     “I just wanted to find out if you recalled an incident which took place in’ 58.”
 
     “’58? What incident?”
 
     “Were you in Calcutta right through that year? That’s the first thing I’ve got to know.”
Explanation:
 
Bepin remembered the fact of attending Puja with his friend Haridas in October 1958. Still, he wanted to double-check the Ranchi trip, as Ghose had stated. So, he decided to speak with Dinesh. According to Bepin, a talk with Dinesh would help in resolving the uncertainties on the Ranchi trip that had been bothering him for some time.

So, Bepin Babu dialled Dinesh Mukerji's number shortly before noon. Since Bepin was afraid of Dinesh's sarcastic remarks, Bepin thought that solving the confusion over the phone would be more convenient than seeing him in person. As a result, he decided that calling Dinesh was preferable.

Two-three-five-six-one-six was the phone number of Dinesh. Bepin Babu then called Dinesh.
 
Bepin's call to Dinesh.png
Bepin's call to Dinesh
 
When he picked the call, Bepin started the conversation by greeting Dinesh. "Is that Dinesh? This is Bepin here," said Bepin. Dinesh and Bepin began a conversation. Immediately, Dinesh inquired Bepin as to why he had called.

Bepin replied that he called Dinesh as he was curious to know if Dinesh had any memories of an incident occurred in 1958. But, of course, Dinesh didn't expect such a question from Bepin. So, he asked Bepin as to which incident he was referring to in 1958. Hearing that, Bepin no longer had the patience to wait for any further question or answer, and he directly questioned Dinesh, "Were you in Calcutta right through that year?".

Bepin wanted to double-check with Dinesh since his meeting with Ghose was upsetting him. Despite the fact that Bepin was not a thick-skinned person and was expecting an unpleasant remark from Dinesh, he opted to phone Dinesh to confirm the Ranchi trip.
 
Also, Bepin felt that calling Dinesh for clarification rather than seeing him in person would be safer. Bepin knew Dinesh would keep him in an awkward situation if Bepin met and explained his confusion in person.
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
Embarrassing Something that makes you ashamed or feel nervous
2.
Thick-skinnedSomeone who is not offended by criticisms or satirical remarks
3.
BotherTo annoy or worry somebody
4.
Awkward Something difficult to deal with
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.