Episode 4

As the team process the aftermath of the explosion, Perez sets his sights on Connor as the bomb-maker and prime suspect. Rachel Cairns is outraged, believing her son is the victim not the perpetrator.

Perez's team interview those closest to Connor in search of any extremist beliefs. While Jamie, Murry and Lloyd reject the notion Connor is capable of violence, a despairing Danny admits environmental issues had stirred up anger in his son.

Elsewhere, Sandy tries to fill in the missing pieces about the body found in the voe - William Rodgers, a US citizen. Sandy discovers William worked in the energy industry but his links to Shetland remain unclear and the reason for his death a mystery.

With her family in turmoil, Abbie grows suspicious of Martin the photographer, who is showing an unhealthy interest in the case. Enlisting the help of Clana, she steals Martin's SD card and is stunned by the content.

The investigation takes a chilling turn when another body is discovered at the foot of a cliff. The scene suggests suicide, but the post mortem reveals an altogether more disturbing reality.