For a couple of days afterwards Byomkesh didn’t bring this case up at all. I could guess at his state of mind, so I didn’t urge him either. On the evening of the third day he started speaking of his own volition. Haphazardly, talking almost to himself, he began, ‘There is a phrase in English—vengeance coming home to roost—that is what happened to Debkumarbabu! He had wanted to kill his wife, but such was the will of fate that both times he aimed his lethal arrows, they struck his son and daughter, who were dearer than life to him.

‘Quite unexpectedly, Debkumarbabu had come upon an extraordinary invention. But due to a lack of funds, he was unable to make proper use of it. With an invention such as this, you cannot apply for a patent, because it has no value in the commercial market. But if war-prone, expansionist nations like Germany, Japan or France ever got wind of the formula, they would immediately start producing this lethal poison in their laboratories. The inventor wouldn’t be able to do a thing and he wouldn’t stand to gain anything out of his invention.

‘So Debkumarbabu kept it all under wraps. He needed funds badly because much experimentation was needed to find out all the uses of the poison. But where was the money? In order to conduct such a huge experiment in complete secrecy, he would need his own laboratory, and that requires massive resources. Where would so much money come from?

‘Meanwhile, at home, Debkumarbabu’s wife was making his life quite miserable. Those who are involved in rigorous cerebral activities require some peace on the domestic front— but this was completely lacking in his life. The company of his finicky, unsympathetic and prattling wife was driving him around the bend. Debkumarbabu is not a violent person by nature. If he was given a peaceful atmosphere in which he could pursue his scientific activities, he would want nothing else. From the love he bore for his children, one can imagine that he has a very caring nature. His second wife, had she tried, could have also received her share of his affection. But she was made in a different mould. In fact, Debkumarbabu had begun to hate the very sight of her.

‘A man does not usually have a desire to kill his wife; when he is driven to this extreme, it is because he has reached the end of his tether. Debkumarbabu too had come to a breaking point. Then the deadly poison came into his possession. Here was a way of disposing of his wife. Deep in the recesses of his mind, he began to hatch a plot.

‘Then he saw the advertisement put out by the insurance company for joint life-insurance policies—the husband and wife could take out the policy together and when one of them died, the other one would get the money. Now all his doubts were resolved. Where would he get such an opportunity again? If he could take out that policy and then kill his wife with the poison he had invented—it would be like killing two birds with one stone; he would get the money he wanted and his wife too would die in a manner which would be impossible to detect.

‘Debkumarbabu took out a policy for fifty thousand rupees at one shot, and then began to bide his time. It wouldn’t do to rush things—the insurance company would get suspicious. A year went by. Finally, he made up his mind to shoot his deadly arrow during the Christmas vacations.

‘The poison he had invented had explosive properties; in its normal state it was quite harmless, but once it came in contact with fire, its lethal powers evolved in the form of a chemical vapour. If a whiff of that vapour entered someone’s nose, death was certain and instantaneous.

‘Debkumarbabu figured out an ingenious plan for targeting his wife with this poison. Such ingenuity is only possible from a scientific mind. He coated some matchsticks with the poison. I do not know the process by which he did this, but the result was that whoever struck one of these matchsticks would inhale the vapour and die immediately. Having got these matchsticks ready, Debkumarbabu began to prepare for the science congress in Delhi. Gradually, the day of his departure drew close. At some point, he placed one of these matchsticks in the matchbox that was kept in his wife’s room, and left for Delhi. He knew that every night his wife lit the lamp by striking a match from that matchbox—this wasn’t for use elsewhere. Today or tomorrow, at some point the lady would strike the fatal match. Debkumarbabu would be far away in Delhi— nobody would suspect that this could be his handiwork.

‘Everything was perfect, but destiny begged to differ. Rekha went to light the stove, couldn’t find the matches, borrowed her stepmother’s matchbox and struck the fatal matchstick.

‘Debkumarbabu returned from Delhi. After this calamity, his heart hardened against his wife more than ever before. He became stubborn—since his daughter had been killed, she too would have to die. A few days passed. Again he kept one poisoned matchstick in the matchbox and prepared to leave for Patna.

‘But calamity struck again—this time even before Debkumarbabu had a chance to leave. Habul was in the habit of smoking; perhaps he was out of matches and so he took some matchsticks out of his stepmother’s matchbox and went for a stroll. Then...

‘Debkumarbabu had churned the high seas of science and had come up with what he thought was the most wonderful of inventions. Little did he know that he had only succeeded in dredging up the most poisonous, the most satanic of vipers. His little flames of poison ruined everything that he held dear.’

Byomkesh heaved a deep sigh and stopped.

After a pause, I asked him, ‘Tell me, when did you first suspect that Debkumarbabu was the culprit?’

‘The