As the investigation draws to a close, Tosh and Calder try to unravel the mystery at the heart of the Bains. The identity of the killer lies in the reason why Ellen left Shetland.
Unnerved by her discovery, Calder decides to stay on in Shetland. Tosh welcomes the support, as the revelation of a tattoo sends the case in a sinister new direction.
Calder and Tosh must work together to find the armed killers and prevent further disaster. Howell and Nowak take refuge with a local and wait for a means of escape.
