In 1925, the progressive girl Zhongli (played by Tang Yan) was inspired by her patriotic enthusiasm to revitalize the nation and signed up for the special training class during the first cooperation between the Kuomintang and the Communist Party. She was assigned to a group with Luo Yifei (played by Wang Di) and Tan Ruiling (played by Lv Yi), and they forged a deep friendship during the brutal training and execution of tasks. During an operation, Zhongli unexpectedly met her superior, elite agent He Junfeng (played by Luo Jin), but the two people with different personalities burst into love like fate. Because of the special operations team's quota for external assignments, Luo Yifei and Zhongli turned against each other; the weak Tan Ruiling was used by Gao Yishan, the highest commander of the special training class. Subsequently, the three girls successively entered the special operations team chaired by Gao Yishan and made significant contributions to the Northern Expedition. However, the action team's elimination of dissidents made Zhongli doubt the justice of the action team. His superior He Yun sacrificed herself to protect Zhongli, which shocked and educated Zhongli. In the most difficult environment, he fought alone and protected a large number of progressive people. He also saved Luo Yifei and Tan Ruiling many times, exposed Gao Yishan's reactionary face, and helped them find the right direction in life...