Theory:

     Dr Chanda shook his head.
 
     “You know what, Mr Choudhury,” he said. “I’ve never had to deal with a case such as yours. Frankly, this is quite outside my field of experience. But I have one suggestion. I don’t know if it’ll work, but it’s worth a try. It can do no harm.”
 
     Bepin Babu leaned forward anxiously.
 
     “As far as I can make out,” said Dr Chanda, “And I think you’re of the same opinion — you must have been to Ranchi, but due to some unknown reason, the entire episode has slipped out of your mind. What I suggest is that you go to Ranchi once again. The sight of the place may remind you of your trip. This is not impossible. More than that I cannot do at the moment. I’m prescribing a nerve tonic and a tranquilliser. Sleep is essential, or the symptoms will get more pronounced.”
 
     Bepin Babu felt somewhat better the next morning.
 
     After breakfast, he rang up his office, gave some instructions and then procured a first class ticket for Ranchi for the same evening.
Explanation:
 
The doctor was confused since he was dealing with a situation like Bepin's for the first time. He also lacked expertise dealing with problems such as partial memory loss. Nevertheless, he told Bepin that he had a suggestion for him to do which would not harm him in any way.

The doctor recommended working out his suggestion for betterment. Bepin leaned in closer to the doctor, tensed, and impatiently awaited his advice. Finally, the doctor expressed his point of view. He told Bepin that, despite the fact that Bepin had visited Ranchi, the entire event had gone from his mind for some unknown reason. So, the doctor asked him to visit Ranchi once again since the sight of the place might trigger recollections of his journey.

Though the doctor was not sure that Bepin would regain his consciousness after visiting Ranchi, it was the only solution he could suggest Bepin. And he prescribed Bepin a nerve tonic and a sedative to reduce his anxiety. Also, the doctor warned him to have a proper sleep. Else, lack of sleep may result in worsening Bepin's condition. Bepin consumed the medicine prescribed by the doctor.
 
Bepin Babu felt somewhat better the next morning. After breakfast, he called his workplace, issued some instructions, and then booked a first-class ticket to Ranchi for the same evening.
 
Bepin's journey toward Ranchi.png
Bepin's Ranchi journey
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
Anxious Worried that something bad will happen
2.
Tranquilliser/SedativeA drug that makes you sleep given to someone when they are nervous or anxious 
3.
ProcureTo obtain something without difficulty
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.