Train

Seo-kyung finds the keepsakes that were gone 12 years ago at a murder scene in the skeleton.

Seo-kyung is murdered by the Mugyeong Station killer. Do-won sees someone unexpected at the station.

Do-won goes to World B and meets Seo-kyung. He's being chased as the suspect of a murder case.

Do-won A starts looking for victims of World A in World B, then has an unexpected encounter.

Do-won and Seo-kyung B are at odds over Kim Jin-woo, the suspect of the missing person case.

The duo chases the culprit of the murder from 12 years ago. Do-won learns about Seo-kyung's past.

Sung-wook falls in front of Do-won and Seo-kyung's eyes. Meanwhile, Do-won A encounters Do-won B.

Do-won's shocked to find traces of the culprit in Do-won B's body and learn about the serial killer.

Min-joon confesses that he was the real culprit of Mugyeong Residence Murder Case from 12 years ago.

Do-won and Seo-kyung waits for train 8210 but it no longer arrives. The two worlds are disconnected.

Min-joon's anger towards Mi-sook begins to tighten Mi-sook's neck. Can Do-won save the day?