' Mal ley ▁( T . R . ▁Knight ) ▁for ▁a ▁consult ▁on ▁his ▁father ' s ▁val ve ▁replacement ▁after ▁George ▁finds ▁out ▁about ▁Bur ke ' s ▁hand ▁trem ors ▁and ▁Crist ina ▁helping ▁him ▁cover ▁it ▁up . ▁H ahn ▁trans fers ▁to ▁Seattle ▁Grace ▁Hospital ▁in ▁the ▁season ▁four ▁episode , ▁" Ha unt ▁You ▁Every day ", ▁after ▁performing ▁a ▁successful ▁heart ▁trans plant ▁at ▁the ▁request ▁of ▁the ▁Chief ▁of ▁S urg ery , ▁Richard ▁Web ber . ▁ ▁She ▁takes ▁on ▁the ▁role ▁previously ▁held ▁by ▁Bur ke , ▁Seattle ▁Grace ' s ▁Head ▁of ▁Card i oth or ac ic ▁S urg ery . ▁H ahn ▁cultiv ates ▁an ▁ant agon istic ▁relationship ▁with ▁Bur ke ' s ▁former ▁prot ég ée ▁Crist ina ▁Yang , ▁ref using ▁to ▁let ▁her ▁scr ub ▁in ▁on ▁sur ger ies , ▁and ▁constantly ▁critic izing ▁her ▁over ly ▁enthus i astic ▁behavior . ▁She ▁later ▁conf esses ▁to ▁Add ison ▁Mont gom ery ▁( K ate ▁Wal sh ) ▁that ▁she ▁is ▁pur pos ely ▁hard ▁on ▁Crist ina , ▁as ▁she ▁rem inds ▁her ▁of ▁herself ▁as ▁a ▁Res ident . ▁ ▁The ▁character ▁def lect s ▁the ▁rom antic ▁attention ▁of ▁fellow ▁att ending ▁Mark ▁Slo an , ▁adm itting ▁that ▁she ▁finds ▁him ▁attract ive ▁but ▁wishes ▁to ▁keep ▁her ▁private ▁life ▁separate ▁from ▁her ▁working ▁life . ▁She ▁also ▁develop s ▁a ▁friendship ▁with ▁Call ie ▁Tor res ▁which ▁becomes ▁tempor arily