Why is the TV series "The Bell of Life and Death" the ceiling of spy war?

"The Bell of Life and Death" is a 20 13 Chinese mainland TV series, directed by Li Huimin and starring Huang Jue, Bian Xiaoxiao, Wang Weiguang and Song Jialing. The play tells the legendary story of the hero Xie's 72-hour speed of life and death in order to save his compatriots and deliver important information. Although the score of this drama is 4.9 on Douban, it is called the ceiling of spy war drama.