The beast cop Ma Seok-do returns—This time, to the Metro Investigations! Seven years after the roundup in Vietnam, Ma Seok-do (Don LEE) joins a new squad to investigate a murder case. Soon, he finds out this case involves busting a synthetic drug and starts to dig deeper... Meanwhile, the guy behind it all—Joo Sung-chul (LEE Jun-hyuk)—doesn’t stop looking for trouble, and the Japanese drug distributors, Ricky (Aoki MUNETAKA) and his gang, come to Korea to join the chaos. Things are just about to get out of hand... It’s time to wipe out the bastards again— If they want trouble, give ‘em trouble!