The Mutations Episode 3

Inspector Chu has a twin brother, Chu Si Ye, who was part of the original investigation. Both brothers are imperial guards, but Inspector Chu was ill when the mission was assigned, so Chu Si Ye went in his place and never returned. Feeling responsible, Inspector Chu has been investigating the plague to find his brother without official authorization. Eventually, Inspector Chu was found out by Eunuch Yang, and fearing he knew too much about the island's happenings, he was captured and detained upon returning from the island. Meanwhile, Bo Yan remains on the island, captured by the locals who are anxious that he may have uncovered their secrets. (Source: Mesutton at MyDramaList)