Shetland 4x6 - Series 4, Episode 6

Troubled by historical DNA evidence results, Jimmy has to facethe fact that Duncan may have been involved in Lizzie Kilmuir'smurder, and potentially Sally McColl's as well. A shockedDuncan is brought to the station for questioning, hurt thatPerez would even think him capable of murder. However, thedetective knows Duncan's lying - perhaps not about the murder,but about something else significant. So when Duncan finallyadmits he had an affair with Donna, it's not long before abombshell is dropped.