Korea in 1909 is about to be absorbed into the Japanese empire. Ahn Jung-geun (Hyun Bin) is a principled man who leads a clandestine group that plots to assassinate Ito, the main architect behind the invasion, at Harbin Railway Station. But when a mission to procure explosives goes awry, Ahn is led to believe that one of their own is an informant for the Japanese. Tensions turn deadly as the threat of a traitor looms all the while the seemingly unstoppable enemy forces hunt them down.