A man has been violently assaulted in his home on the island of South Uist and has been airlifted to hospital. As he is unconscious and unable to give an account of what happened, it's the crime scene that holds all the clues. Detectives from Stornoway make the four-hour journey by ferry and road as they rush to the scene to gather any forensic evidence before it is lost. Back on the mainland, time is also against PC Stephen Cooper as he coordinates a full-scale search operation for a male hillwalker missing in the mountains of Glencoe. The search team receive a glimmer of hope when the walker's rucksack is found, but it doesn't help give any indication of the route that the walker was taking. Police examine the missing man's most recent text messages for clues. On Skye, two crofters are in a long-standing dispute over a shared piece of land, highlighting the tensions which can exist between old and new generations of island residents. Ex-Glasgow copper Sgt Gordon Gray is on hand to manage negotiations. On Shetland, Sgt David Carmichael investigates a complaint of racially motivated abuse at a local chemist. His investigation leads him to the door of a suspect who is well known to the police.