Detective Inspector Jimmy Perez investigates murders on the Shetland Islands, where the small population, the ferry timetable and the weather all shape how an inquiry can be run. The BBC One series began in 2013 as an adaptation of Ann Cleeves's novels, with Douglas Henshall in the lead and Alison O'Donnell as DS Tosh McIntosh; from the eighth series Ashley Jensen took over as DI Ruth Calder. Cases run across whole series rather than single episodes, and the location work in Lerwick and the outer isles is a large part of the appeal.