This is a murder case that occurred in a small northwest town. The deceased was a highly educated and beautiful teacher from a coastal city. As the case unfolds, several criminal suspects gradually appear in everyone's sight: the female teacher's duplicitous colleague, her wealthy second-generation mayor lover, the mayor's second-generation official wife, a drug dealer who has been hiding for many years, and the family of the girlfriend who died because of her. Who killed her? The male protagonist Xue Tiejun is very eager to know the answer, because this case also hides the reason for his wife's sudden death, as well as their family's deepest secret. The case became increasingly clear, but Xue Tiejun found himself truly alone and faced an important decision in his life. This is a story that questions human nature. What is morality? Sometimes it seems that it does not exist, but closing the door of morality may open the door of death to darkness.