Wire in the Blood S04E03 - Hole in the Heart

Tony and Alex investigate a serial killer who leaves behind a trail of two bodies at every crime scene. Tony suspects that the murderer may have a link to religious zealotry, but struggles to see beyond his own lack of personal faith and religious disinterest. When Alex discovers the killings may be related to a disparate group intent on cleansing the human race, Tony is forced to see the light to crack the case.