The film begins in November 1942 in Calcutta, where a group of Chinese men from the Green Gang are smuggling opium from the docks. An unknown gang attacks them, and one of them brutally blinds the Chinese gang’s leader.
In January 1943, Ajit Kumar Banerjee (Anand Tiwari) approaches Byomkesh Bakshi (Sushant Singh Rajput) asking him to locate his father, Bhuvan Banerjee, who has been missing for two months. Byomkesh rejects the request initially but later takes on the case. The following day, he visits the lodging house Bhuvan Babu resided in, run by Dr. Anukul Guha (Neeraj Kabi), a physician. Byomkesh also meets Kanai Dao (Meiyang Chang), an opium seller and Ashwini Babu, Bhuvan Banerjee’s roommate.