Perfect Murder in Zero Crime City

In 2179 AD, Blue Star entered the "little freeze period". The mid-to-high latitudes of the northern hemisphere were reduced to permafrost, and most cities were abandoned. Frostspire City is a closed dome city built by humans on the tundra. It relies on deep geothermal heat and shale gas to support its operation. The entire city is covered by a giant insulated dome. It has a population of 2.8 Million. Access to the city is strictly controlled and it is almost isolated from the world. It is the only large human settlement in the north. Three-tier urban layout: Jingding District, the suspended city at the core of the dome, is the Hanshu headquarters and the gathering place for the powerful and elite. Residents enjoy the highest level of security and resources, and ordinary people cannot enter it for life; The ring corridor area is a mid-rise urban area surrounding the crystal dome. Factories, companies, and ordinary residential areas are located here. It is the main gathering place for employees, skilled workers, and small businessmen; The Ballast District is an abandoned old city on the edge of the dome. The heating is interrupted and surveillance is sparse. Officially, it is claimed to be uninhabited, but in fact it is filled with low-class refugees, fugitives, and people who have been eliminated by the system. Under the giant insulated dome, the "Crystal Curtain" global sensing system covers every inch of space. Gait, voiceprint, and body temperature are captured and archived in real time. Officials have declared that the city has entered a "zero crime era." However, there are fatal loopholes hidden deep in the system that have never been disclosed: a "calibration gap" that occurs every 48 hours. Within 4 minutes and 17 seconds, all peripheral monitoring units are collectively offline, and the data does not exist, becoming an absolute blind spot for a perfect crime...