Instead of rambling on, however, Chen lapsed into silence all of a sudden.

‘In your notes on another serial murder case,’ Yu said, after having waited for a minute for Chen to go on, ‘you also talked about something like a ritual with its inner logic comprehensible only to the murderer, even though the choice of victims seemed to be so uncalled for and unrelated. But ritual or not ritual, it will be too much of a blow to the bureau when another victim falls this week. For a cycle of seven days, we have only two days left.’

‘Yes, for a cycle of seven days,’ Chen said, echoing, ‘and he’ll act before the week is over. Exactly seven days. There’s a sort of ritualistic offering that Chinese families – most Chinese families – have to make after the death of a family member.’

‘Seven-seven!’

‘Exactly! According to the folk belief, the soul of the deceased is unwilling to leave the human world, so it lingers here, as if still functioning – at least partially functioning – like in life. Seven days after one’s passing away, his or her family members will gather together for a special meal dedicated to the dead, along with the burning of candles and incense, and sometimes of the nether world money too, and then the meal will be enjoyed by the living family members, like in a family reunion with the deceased. The ritual will be repeated on the next seventh day, until the end of the seventh week. By that time, the soul of the deceased is said to be able to leave in contentment. With the deceased so far away from home at the end of the seven weeks, the family does not have to provide the ritual service any more, though some still do so, like at a hundred-day anniversary, or ten-year anniversary, or some other variation.’

‘Yes, Peiqin has told me about it. The service at Longhua Temple was the twenty-year ritual for Peiqin’s parents having left the world, more or less the same logic as with the seven-seven.’

‘So the murderer strikes out at a seven-day interval.’

‘That’s true, but not exactly at a seven-day interval. Let me double check,’ Yu said in a hurry, taking out his phone to pull out a chart. ‘Eight days between the first and second, six days between the second and the third, and then seven days.’

‘That’s more than understandable, I think, if we take into consideration the difficulty of his killing exactly on the seventh day at those central locations. After all, to commit the crime may not be as easy as to prepare a meal at home. The killing of the second victim might not have been performed on the seventh day for some unforeseeable reason, given the circumstances. So he had to act on the following day. Then for the third victim, it was after six days – to average it to seven days.’

‘That’s right. So you’re really talking about the scenario of a sociopath killing for the ritual of seven-seven this coming Friday?’