Qin Hai had something he hadn't said to Xiao Nannan: based on the color of the bloodstains around Xue Rong's mouth and the peculiar smell, he not only could determine that Xue Rong had died from poisoning but also knew that he had died from the latest restricted overseas delayed poison, TL.
The defining feature of this poison named TL is that it can cause death within a set time, with symptoms extremely similar to a sudden heart attack; once it kicks in, there is virtually no antidote. This poison's concealment is incredibly strong, and if it weren't for Xue Rong vomiting blood out of anger, which led to his premature death, even Qin Hai wouldn't have detected it so quickly.
The developers of this poison were the IN Organization, the very same evil group Qin Hai had always intended to eradicate before his rebirth.