Blue Lightning (Shetland Island #4) by Ann Cleeves; 2011. Softcover.

Blue Lightning is the fourth book in Ann Cleeves' Shetland series featuring Detective Jimmy Perez.

With the autumn storms raging, Fair Isle feels cut off from the rest of the world. Trapped, tension is high and tempers become frayed. Enough to drive someone to murder . . .

A woman's body is discovered at the renowned Fair Isles bird observatory, with feathers threaded through her hair. The islanders react with fear and anger. Detective Jimmy Perez has no support from the mainland and must investigate the old-fashioned way. He soon realizes that this is no crime of passion - but a murder of cold and calculated intention. There's no way off the island until the storms abate - and so the killer is also trapped, just waiting for the opportunity to strike again.