Pang Hong Mei --- Peng Xiao Ran
Pang Hong Mei, a police officer in the Special Task Force, is the partner of Ji Danyang, her first love. She has a gentle and kind personality. As a police officer entrusted with the responsibility of guarding national secrets and carrying out important missions, her identity and duties make her a prime target for enemies. Through countless attempts and relentless efforts, she eventually succeeds in defending the security and interests of her country. However, in the course of her professional career as a specialist, she has been ambushed by enemy agents, and unfortunately, the covert operation fails.
Ji Dan Yang --- Liu Xue Yi
Ji Danyang, a mathematics expert who returned from studying abroad, participated in the "Water Drop" plan. He has been operating undercover within hostile forces, gathering intelligence from within enemy ranks. Pang Hong Mei and Ji Danyang form a bond through their shared mission. From initial misunderstandings to being moved by Pang Hong Mei's sincerity and intelligence, the two of them go through various challenges but remain steadfastly together. Their love endures the baptism of war, becoming even stronger and more resolute.
Bai Hui --- Jian Ren Zi
Infiltrating enemy ranks, Bai Hui unknowingly walks towards her own demise while being manipulated by the enemy. At a critical moment, she is fatally struck by Hong Mei and plunges into darkness completely. Desperate, Bai Hui plots to deceive Ji Danyang and tries to make him stay with her forever. However, Ji Danyang once again persuades Bai Hui to turn back, but she refuses to listen and persists in her downward spiral.
Bai Ming Han --- Ding Yong Dai
Bai Ming Han is a special agent of the Kuomintang (Nationalist Party) known as "Ghost Owl." Pang Shi Zhao guides him onto the path of revolution and instructs him to send a message to the People's Liberation Army to rescue the individuals held captive in the Little Grey Building. However, the message fails to reach its destination as Pang Shi Zhao tragically sacrifices herself. Despite being a special agent of the Kuomintang, Bai Ming Han has been secretly helping the Communist Party. After the sacrifice of Pang Shi Zhao, Bai Ming Han vows to avenge her. In the final moments of his life, Bai Ming Han finally reveals his true identity.
Chen Dong Sheng --- Li Xin Ze
Chen Dong Sheng, the head of the Special Protection Team responsible for the personal safety of the expert group, possesses exceptional leadership skills. No matter how difficult someone may be to handle, once they are in his hands, they will undoubtedly be brought under control. As the captain of the action team tasked with protecting the "Water Drop Project" and directly engaging with spies, he is willing to sacrifice his life to fulfill his mission and duties. Regrettably, he ultimately falls victim to the gun of a spy.
