In episode 12, titled 'The Murder', the key event that triggers the investigation is the shocking murder of a character closely connected to the protagonist, Seo Jin. This event sets off a chain reaction of emotional turmoil and drives Seo Jin to uncover the truth behind the murder.

Throughout episode 12, Seo Jin's emotional state is marked by despair and determination. Initially, he is overwhelmed by grief and guilt over the murder, feeling a deep sense of loss. As the episode progresses, his resolve strengthens, leading him to take action to find the murderer, showcasing his transition from victim to an active seeker of justice.

In episode 12, Han Ae Ri plays a crucial role as she becomes a key ally to Seo Jin. Her insights and emotional support help him navigate the complexities of the investigation. Ae Ri's character also grapples with her own fears and motivations, which adds depth to her relationship with Seo Jin as they both seek closure.

During the investigation in episode 12, several significant clues are revealed, including a mysterious phone call that Seo Jin receives, which hints at the identity of the murderer. Additionally, evidence found at the crime scene leads to unexpected connections between the victim and other characters, deepening the intrigue and raising the stakes for Seo Jin.

In episode 12, the theme of time is explored through Seo Jin's desperate attempts to alter the past and prevent the murder from happening. The narrative delves into his internal struggle as he grapples with the limitations of time, showcasing his emotional turmoil and the weight of his choices as he races against the clock to uncover the truth.