▁( A aron ▁McC us ker ), ▁with ▁whom ▁she ▁co - run s ▁the ▁pub . ▁Season ▁ 5 ▁sees ▁her ▁becoming ▁increasing ly , ▁al beit ▁grud ging ly , ▁more ▁integrated ▁with ▁the ▁Mag u ire ▁family ▁and ▁their ▁somewhat ▁violent ▁way ▁of ▁life . ▁Kar en ▁suff ers ▁a ▁mis car riage ▁early ▁in ▁season ▁ 6 ▁and ▁very ▁soon ▁after , ▁her ▁changing ▁behavior ▁and ▁the ▁loss ▁of ▁their ▁child ▁starts ▁creating ▁a ▁large ▁r ift ▁in ▁their ▁marriage . ▁As ▁she ▁and ▁Jam ie ▁argue ▁over ▁shared ▁ownership ▁of ▁The ▁J ockey ▁and ▁other ▁problems , ▁Kar en ▁finds ▁herself ▁drawn ▁to ▁her ▁sister - in - law , ▁M andy ' s ▁( Sam anth a ▁S idd all ), ▁ab us ive ▁boy friend ▁Joe ▁P rit ch ard ▁( Ben ▁Batt ), ▁and ▁has ▁sex ▁with ▁him ▁shortly ▁after ▁Jam ie ▁moves ▁out . ▁Joe ▁becomes ▁increasing ly ▁cont rolling , ▁threaten ing ▁to ▁reve al ▁their ▁affair , ▁and ▁makes ▁a ▁failed ▁attempt ▁to ▁buy ▁out ▁Jam ie ' s ▁portion ▁of ▁The ▁J ockey . ▁During ▁this , ▁the ▁Mag u ires ▁find ▁out ▁Joe ▁has ▁been ▁phys ically ▁ab using ▁M andy , ▁and ▁Jam ie ▁is ▁almost ▁sent ▁back ▁to ▁prison ▁after ▁brut ally ▁be ating ▁him . ▁When ▁Jam ie ▁moves ▁back ▁in ▁with ▁Kar en , ▁she ▁is ▁able ▁to ▁end ▁her ▁affair ▁with ▁Joe ▁by ▁threaten ing ▁him ▁that ▁if ▁she ▁claims ▁to ▁the ▁Mag u ires