Oh Ji-hyuk shows significant growth in this episode as he grapples with the moral complexities of his job. He becomes more empathetic towards the victims and their families, reflecting on his own past mistakes and the weight of his responsibilities as a detective.

Jang Seok-jin plays a pivotal role in the investigation as he provides critical insights based on his experience. His analytical skills help the team connect the dots between various pieces of evidence, and he often serves as a voice of reason, guiding the younger detectives through the emotional turmoil of the case.

In episode 4, the detectives uncover a crucial piece of evidence when they find a hidden camera in the vicinity of the crime scene. This camera provides them with video footage that reveals the moments leading up to the murder, shedding light on the victim's last interactions and the potential suspects.

In this episode, Kim Do-jin faces personal challenges as he struggles with the pressure of the investigation while dealing with his own family issues. His emotional state is further complicated by the haunting memories of a past case that still affects him, leading to moments of self-doubt and frustration.

The episode explores the theme of justice as the detectives confront the harsh realities of their work. They face obstacles that test their commitment to uncovering the truth, and their determination to seek justice for the victim becomes a driving force, highlighting the emotional toll that such cases take on them.