In June 1941, Suzhou City had fallen to the Japanese invaders for nearly four years, and the claws of the Wang Puppet Government were raging in Suzhou City.The young master of the Gu family, Gu Yizhong, was originally an architect with outstanding talent and learning. After studying abroad, he founded the Construction Society in Suzhou, trying to make a contribution to Chinese architecture like his senior Liang Sicheng.Although he is a scholar, Gu Yizhong was born in a military family and has a patriotic heart. Under the guidance of his friend Xiao Junxia and his lover Xiao Ruotong, two party members, he secretly helped organize the Iron Blood Action Team and participated in the national salvation operation.The Jagged Action Team secretly planned to rescue Taro Nakanishi, an underground member of the Communist International who was imprisoned in Yiyuan at No. 90 of the Wang Puppet Secret Service Station.Yiyuan has a complex layout and tight defenses, making it difficult to rescue people. However, Gu Yizhong relied on the architect's strong sense of space to restore the floor plan of Yiyuan from memory and planned a perfect escape route.Unexpectedly, during the execution of the mission, the Iron-Blooded Operation Team was ambushed by spies and almost the entire army was wiped out. Xiao Junxia was in danger of covering Gu Yizhong's escape. Gu Yizhong also protected Xiao Ruotong who was assisting outside. Unfortunately, he fell into the hands of Zhou Zhifei, the commander of Agent No. 90..At the same time, another wave of people on the 90th went to arrest underground party members. The experienced Hu Zhiping sensed the danger in advance and moved his pregnant wife Gu Huizhong early.To ensure safety, Gu Huizhong returned to Gu Yuan after ten years of absence.