In a quiet town, in-depth research on criminal psychology is closely linked to a serial murder case.This case attracted the attention of FBI agents Holden and Bill, who discovered that the victims were all elderly grandmothers with pet dogs.The psychological motives hidden behind the case confused the two people, so they decided to seek help from experts in the psychological field.

Dr. Wendy Carr, a renowned expert in the field of criminal psychology, was very interested in their research.She invited two agents to a university in Boston, Massachusetts, and shared with them the latest cutting-edge psychological research.Dr. Wendy suggested that recording conversations during interrogations and converting them into text would help the research progress.She also encouraged Holden and Bill to devote themselves to this research full-time and publish the research process or results to the world.However, Bill believed that the FBI would not approve of such a full-time research approach, so he politely rejected Wendy's suggestion and asked that the research be kept confidential.

Just as the two were planning the teaching tour route, an emergency phone call broke the calm.Police officer Roy Carver, who had handled similar cases, reported that another old woman was attacked and murdered for no reason.The escalation of the case made the two realize the seriousness of the problem.After obtaining permission from their boss, Sheppard, they quickly rushed to the Sacramento Police Department.

Through the investigation of the scene and the collection of clues, Holden overturned the previous conclusion that the suspect was a teenager.After discussion, they targeted Dwight, a man in his thirties who suffered from social disorders.In Dwight's residence, they found traces of a pet dog and a mother who was hostile and insulting to her son.During the interrogation, Dwight admitted his crime. Because he could not bear the insult from his mother, he chose to attack the innocent old woman.

Although the case was solved, the two detectives' research was not over.They wanted to interrogate new research subject Miller, but Miller refused to communicate.So, they turned their attention to Ed Campbell.Through the psychological offensive and the participation of Dr. Wendy, Ed gradually lowered his psychological defense.He admitted that everything he did was based on revenge for his mother's insult.Ed revealed that he buried the heads of six girls outside his mother's bedroom window, hoping to use their eyes to stare at his mother day and night.

After the interrogation, Bill admired Holden's eloquence and believed that they needed Dr. Wendy's expertise to analyze this complex case.After receiving the invitation, Dr. Wendy rushed to the FBI headquarters without hesitation to discuss the next research plan with the two agents.