▁k iller ▁is ▁" Mr . ▁Sc r atch ", ▁who ▁ta un ts ▁the ▁team ▁by ▁turning ▁over ▁the ▁real ▁" C rim son ▁King ", ▁who ▁was ▁tort ured ▁to ▁the ▁point ▁he ▁no ▁longer ▁rem embers ▁who ▁he ▁was . ▁After ▁that , ▁Al vez ▁dec ides ▁to ▁join ▁the ▁B AU ▁full ▁time ▁and ▁was ▁Hot ch ' s ▁last ▁h ire . ▁Al vez ▁has ▁a ▁Belg ian ▁Ter v uren ▁dog ▁named ▁Ro xy ▁( wh om ▁Gar cia ▁thought ▁at ▁first ▁was ▁his ▁human ▁girl friend ) ▁and ▁served ▁in ▁Ira q ▁as ▁an ▁Army ▁R anger ▁prior ▁to ▁joining ▁the ▁F BI . ▁ ▁Stephen ▁Walker ▁( D am on ▁Gu pton ), ▁super vis ory ▁special ▁agent ▁( season ▁ 1 2 ) ▁ ▁Walker ▁is ▁a ▁super vis ory ▁special ▁agent ▁with ▁the ▁B AU . ▁Walker ▁was ▁a ▁member ▁of ▁the ▁Be havior al ▁Analysis ▁Program . ▁He ▁was ▁contact ed ▁by ▁Em ily ▁Pr ent iss ▁( P aget ▁B rew ster ) ▁about ▁joining ▁the ▁B AU ▁to ▁assist ▁in ▁the ▁man h unt ▁for ▁Peter ▁Lewis , ▁a ▁k ▁a ▁" Mr . ▁Sc r atch ". ▁Walker ▁is ▁an ▁experienced ▁profil er ▁with ▁about ▁ 2 0 ▁years ▁under ▁his ▁bel t ▁and ▁a ▁member ▁of ▁the ▁F BI ' s ▁Be havior al ▁Analysis ▁Program ▁before ▁his ▁transfer ▁to ▁the ▁B AU . ▁He ▁is ▁married ▁to ▁a ▁woman ▁named ▁Mon ica ▁and ▁has ▁two ▁children ▁with