Mukyeong Train station has been closed and abandoned since 2015. The land only has stray cats and weeds growing all over the area.

On the same night, Seo Do Won and Han Seo Kyung's father died in separate places. Do Won's father died due to a road accident, but a necklace was found in his pocket, while Seo Kyung's father died due to being strangled by someone using a necklace that was lost in their property, taken by the murderer. Do Won and Seo Kyung are now both orphans.

At present, they are now working as professionals in their field of interest. Do Won is a detective while Seo Kyung is a prosecutor. Do Won works hard to put criminals in jail while Seo Kyung protects people from injustice put evildoers in prison.

While trying to arrest a lawbreaker, Do Won found skeletal bones at the railways of Mukyeong station. The following day, the crime division department and other forensic experts searched the whole area and found more human bones buried in different sites.

Han Seo Kyung checked with the forensic team and found out that most of the victims were killed using heavy objects that broke their skull. She is curious if the case is related to her father's unresolved death for the past twelve years.

A video and fingerprint led them to Lee Sung Wook, a mentally disabled resident of Mukyeong. Do Won went to his house and questioned his mother. She is the stepmother of Seo Kyung, who took all his father's insurance money during his death.

Do Won found traces of Lee Sung Wook's candy wrapper around the murder scene. It seems that Sung Wook had been in the area. The forensic team checked his fingerprint, and it matched where they found one of the victim's items.

Do Won went to the abandoned station to find more tips and realized that another victim is buried and hidden somewhere. Seo Kyung arrived and went to search together with Do Won. They chose to search separately to find the body.

It was late at night. While walking around the railways, Do Won fell to the ground unconscious when someone hit his head. Sung Wook arrived and used a spade to crush on Do Won's head. Seo Kyung entered an abandoned warehouse, and as he opened one of the covered buckets, she saw a dead woman hidden in the black bag.

She then tried to contact Do Won, but he couldn't be reached. Sung Wook arrived in the area. She tried to hide, but Sung Wook found her and strangled her.

Do Won tried to open his eyes and felt the blood from his head. He saw an incoming train, and he jumped away from the railway to save himself.

He walked and found Seo Kyung, and he wrestled with Sung Wook.

Seo Kyung wanted to kill Sung Wook, as she assumes that he is responsible for his father's death. Do Won explained to her that it wasn't Sung Wook who killed her father. For the past twelve years, Do Won kept the secret from Seo Kyung about the necklace found in his father's possession.

He couldn't tell her the truth because it breaks his heart. Mrs. Oh, the private investigator who handled the case, decided to keep the secret between them.

During middle school, Do Won struggled with his studies because of his drunkard father. Mrs. Oh saw how hard-working he is and wanted to help him after his father died. Do Won and Seo Kyung lived under Mrs. Oh's house and cared for each other while growing up. Seo Kyung finished her college because of Do Won's help.

The dead body that was found at the station was identical to a person who is alive and has all the same personal information. Lee Sung Wook was arrested and was brought to the station.

The next day, Seo Kyung tried to question Sung Wook about the incident at the station. He mentioned about a train that is coming and the rain is the sign when it arrives.

Seo Kyung was curious and went ahead to check if it was true. While walking along the railway, a train's bustling sound arrives with full lights along with it. A man came out and threw a big black bag. After a while, Seo Kyung opened it and saw a dead body inside.

A gun was pointed at her head, and when she looked up, a gunshot echoed that night.

Do Won was informed that Seo Kyung went to Mukyeong station alone. He rushed to the place and found the lifeless Seo Kyung, covered in blood.