"If cyanide is taken orally, it causes ulceration of the oral mucosa and a very strong odor in the mouth. But only the victim's outer lips show those signs. The inner walls of his mouth don't. In other words, he died of cyanide poisoning, but the poison... wasn't taken orally!"
What puzzled Song Ning was that cyanide was uncommon, yet this was not the first time she had seen a body poisoned by it.
The previous time had been on the train.
Lu Ming said, "The detectives have already examined the scene and collected traces. They're comparing and verifying them now. The forensic examiner has only performed a preliminary examination. Further tests will have to wait until the body is taken back to the laboratory.
"But based on what we know so far, the degree of rigor mortis lets us establish the time of death: between one and three this morning."
Song Ning nodded in agreement.
Lu Ming continued, "It's the National Day holiday, but according to his colleagues, Chief Engineer Zhou rarely took holidays off. Several people from the technical department worked overtime with him yesterday, but they all left early. The last one left at six in the evening. Only Chief Engineer Zhou stayed here!
"And the crucial point is that this room's door was locked from the inside!"
"How did the first person to discover the body get in?" Gu Zheng asked.
"Two technicians working under Chief Engineer Zhou discovered the body. Since they were working overtime, they didn't have to come in at the usual time. The first arrived around ten. He rang the bell outside, but no one opened the door. Then he went to look around the office building, but he couldn't find Chief Engineer Zhou there either.
"While he was looking, he also