青幇
Byomkesh then realizes the drawing he had found is an outline of the Ganga on the Calcutta map and the set of points where the Spring Day campaign is to take place. With Kanai's help, Byomkesh meets with the Green Gang, who help him deduce that Yang Guang has set a deal with the Japanese, who will attack Calcutta at the Spring Day campaign points and take over Calcutta, and in turn will gain control over the opium trade in the city. Byomkesh also realizes that Anguri Devi is Yang Guang's lover, who she has not met in 4 years, who, on Yang Guang's orders, had killed Sikdaar and attempted to seduce Byomkesh, all along being in the dark about Yang Guang's deal with the Japanese. Byomkesh meets Wilkie and requests him to set off all the Air Raid Sirens at 4 AM on the morning of the Spring Day campaign. Wilkie refuses, and Kanai defects to Byomkesh's side, as the latter saved his life from the Green Gang.