第 4 季 共 6 集
播出时间：2018年2月14日
第 1 集 Episode 1
播出时间：2018年2月14日
When Thomas Malone has his murder conviction overturned after 23 years behind bars, DI Perez has to reopen the investigation into the 1994 death of local teenager Lizzie Kilmuir.
第 2 集 Episode 2
播出时间：2018年2月21日
Perez is on the trail of an attacker, Tosh investigates an oil company in the hunt for Sally's killer, and DNA testing in the Kilmuir case yields a surprising result.
第 3 集 Episode 3
播出时间：2018年2月28日
Jimmy questions Donna about the shocking DNA results, Alison arrives in Norway in search of Andreas Hagan, and an unexpected twist leads Perez and Tosh into the murky world of the Norwegian far right.
第 4 集 Episode 4
播出时间：2018年3月7日
Ignoring Secret Service warnings, Perez and Tosh track down Mathias Soderland. Back on Shetland, a beach memorial service is held for Sally McColl.
第 5 集 Episode 5
播出时间：2018年3月14日
Perez must re-assess the investigation in the aftermath of the attack. The MIT arrives on Shetland and sets its sights on Malone. Meanwhile, Tosh begins to have doubts about Lars.
第 6 集 Episode 6
播出时间：2018年3月21日
Season Finale - Troubled by historical DNA evidence results, Jimmy has to face the fact that Duncan may have been involved in Lizzie Kilmuir's murder, and potentially Sally McColl's as well. A shocked Duncan is brought to the station for questioning, hurt that Perez would even think him capable of murder. However, the detective knows Duncan's lying - perhaps not about the murder, but about something else significant. So when Duncan finally admits he had an affair with Donna, it's not long before a bombshell is dropped.
