In a bizarre case operation, police officer Ma Jin (Nicholas Tse) shot and killed the serial killer "General" (Vengo Gao), but was shot through the heart by the other party. His life was hanging by a thread, and he unexpectedly received a heart transplant. After a year and a half, several shocking cases with the same modus operandi as "General" appeared internationally. After recovery, Ma Jin took the initiative to ask for an investigation with Professor Che Jiawei (Liu Qingyun), a professor of criminal psychology. As the case deepened, Ma Jin discovered that Professor Che had a little-known secret, and Professor Che also developed a special interest in Ma Jin after the "heart change". In the process of the two people testing each other and fighting against each other, Ma Jin's wife Mo Xiu (Fan Xiaoxuan) and the mysterious woman Chen Xiangru (Tong Liya) were gradually involved in the incident, and a battle that endangered the lives of millions of people in Hong Kong quietly exploded...