Episode 8 starts with a flashback of Han Tae San (Heo Joon Seok) on the train tracks, and he discovers a man lying down with a briefcase by his side. The man seems to be unconscious and is holding a photo.
When Tae San checks the photo, he was shocked to see that it was him and his brother Han Tae Sul (Cho Seung Woo). The man got up, and Tae San tried to stop him but was distracted by the train, and they went on separate ways. This man is actually Sigma (Kim Byung Chul).
(Photo : JTBC official Instagram (jtbcdrama))