▁is ▁confirmed ▁to ▁be ▁the ▁serial ▁k iller ' s ▁work ▁and ▁the ▁case ▁would ▁get ▁transferred ▁to ▁the ▁Major ▁Case ▁Squad . ▁D ong - so o ▁vis its ▁Sang - do ' s ▁fun eral ▁where ▁the ▁k iller ▁also ▁turns ▁up ▁inform ing ▁Sang - do ' s ▁second - in - command ▁man ▁that ▁it ▁was ▁D ong - so o ▁who ▁actually ▁killed ▁Sang - do ▁with ▁the ▁k iller ' s ▁kn ife . ▁ ▁When ▁T ae - su k ▁and ▁D ong - so o ▁check ▁the ▁k iller ' s ▁car ▁for ▁any ▁evidence , ▁they ▁are ▁attacked ▁by ▁Sang - do ' s ▁hen ch men . ▁A ▁fight ▁ens ues , ▁resulting ▁in ▁the ▁death ▁of ▁Sang - do ' s ▁right - hand ▁man . ▁D ong - so o ▁gets ▁him ▁buried ▁and ▁cle ars ▁the ▁scene . ▁T ae - su k ▁is ▁now ▁assigned ▁to ▁investigate ▁a ▁kid n apping ▁case , ▁and , ▁while ▁solving ▁it , ▁he ▁sp ots ▁the ▁k iller . ▁A ▁ch ase ▁ens ues , ▁but ▁the ▁k iller ▁fle es . ▁Through ▁the ▁for ens ic ▁tests , ▁T ae - su k ▁disco vers ▁the ▁k iller ▁to ▁be ▁a ▁missing ▁person . ▁He ▁inform s ▁D ong - so o ▁about ▁this ▁and ▁lets ▁him ▁hear ▁a ▁voice ▁clip ▁to ▁confirm ▁the ▁missing ▁person ▁to ▁be ▁the ▁k iller . ▁Later , ▁D ong - so o ▁helps ▁a