A Barton Street PC is stabbed when he pursues two robbery suspects into Sun Hill. A black youth, identified as Mark Okin, is found beaten unconscious at about the same time. Carver is assigned to the Okin family in his first role as Family Liaison Officer, but further investigation by CID discovers Mark to be a suspect in PC Brennan's stabbing. Carver is horrified when Daly asks him to use his position of trust with the Okin family to collect evidence against Mark. Evidence soon mounts against John Wilson, the boyfriend of Mark's sister Amy, as Daly suspects that he is responsible for the robbery, stabbing PC Brennan, and assaulting Mark when he refused to take the rap for Brennan's stabbing.