DS De Costa returns to Sun Hill humiliated after being bailed. DC Perkins races to her house, where an increasingly unbalanced Margaret Barnes is planning to commit suicide. In an attempt to prevent her from taking her own life he is stabbed and critically injured. PCSO Laura Bryant is knocked to the ground by a boy running drugs errands. PCs Dan and Stamp track down an inventive graffiti artist who uses cleaning products to produce negative images on dirty walls around Sun Hill. Sgt Smith reprimands receptionist Julian Tavell for gossiping.