This is actually a very simple logic puzzle.
As Song Qingyun said, according to common sense, the person who went in after the murderer couldn't have not noticed that Princess Ling and the others were in trouble.
Xu Jing looked at Song Qingyun with admiration, her lips slightly curved as she said, "There are several possibilities in this situation: one is that the person who went in after the murderer is worried that telling the truth will deepen others' suspicions about him. After all, if everyone says roughly the same thing, and only you say something different, you'll certainly become the most conspicuous one.
Therefore, he or they chose to lie, but in this case, he or they must have some guesses and understanding about who the murderer is.
The second is that the murderer is not among them, and none of them lied; Princess Ling and the others were indeed killed after they left.
The third possibility is that the murderer is Nanny Lu, who went in last.
Fourth is..."
