Season 8, Episode 4:
In 2009 market trader Kathy Green died after drinking drugged coffee. The UCOS team suspect but cannot prove a link with Anthony Gunnell,a man who raped women after doping them with coffee from his refreshment van. They learn that Kathy had an illegitimate daughter who was adopted and whose attempted reconciliation with her mother went badly.
A motley crew of retired police officers re-opens troublesome cases that were never laid to rest.