Why did the old lady in The Masked Hotel kill the mountain bank?

Keigo Higashino's "Masked Hotel" ended with the wedding as scheduled. The wonderful old lady who appeared once before reappeared and still asked for sister service.

It turned out that she was the fourth murderer, deliberately trying to kill the hostess, the receptionist, the old lady who pretended to be blind. When she was young, she lost her child because of the obstruction of the hotel service staff, so she took revenge.

Extended data

abstract

There were three murders in Tokyo. The police inferred from the unexplained sequences left over from all the crime scenes that this was a series of serial killings with advance warning information and launched an investigation.

The metropolitan police searched the elite criminal police officer of Class 1, Hirosuke Xintian (played by Kimura Takuya), who deciphered this number and predicted the location of the next crime, thus speculating that the Cortexia Hotel in Tokyo would be the scene of the fourth murder.

But who is the murderer? Have no idea. Therefore, the police decided to sneak into Kostia, Tokyo to investigate, and Xintian had to pretend to be a receptionist to track down the murderer. He got the guidance of Shangmei Yamanaka (Masami Nagasawa), an excellent receptionist in Kostia, Tokyo.

In the face of a succession of unidentified guests, Xintian, as a criminal policeman, "takes catching criminals as the first priority" and tries to peel off the "mask" of visitors, while Shangmei, as a hotel staff, starts from the principle of "taking the safety of guests as the first priority" and hopes to protect the "mask" of visitors. These two are like fire and water.

Xintian and Shangmei had several conflicts because of their different positions. However, with the advance of latent investigation, as professionals, they gradually understand each other's values and begin to have an incredible trust relationship with each other. In this process, the case developed rapidly. The police and the hotel are desperate, no way back.