A Met detective returns to Shetland on the trail of a vulnerable witness. DI Ruth Calder must team up with Tosh to find the girl before it’s too late.

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.

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.

Tosh believes she has the murderer in custody and tasks the team with finding the evidence to charge. Calder suffers in silence with Jean’s revelation.

Calder initially reels from the awful news, but quickly becomes suspicious. Tosh worries Harry and Donnie with her pursuit of a controversial new theory.

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.

When her friend doesn’t get home one night, Tosh persuades DI Calder – now a resident of the Isles – that something is wrong.

The hunt is on for Ian Bett as a picture of Anton Bergen begins to emerge. Are Calder and Tosh dealing with the revenge of a jealous ex-husband?

As Calder and Tosh wrestle with the revelation of Annie’s past, Noah offers a cryptic clue about the night she was killed.

The team uncovers the sinister truth behind the facility. But the investigation is diverted when Astrid Jakobson goes missing.

Calder and Tosh discover the truth behind Rossi’s mission. They must identify Annie’s killer before he can exact his revenge.

Calder and Tosh turn their focus onto Lisa, until her confession unearths a shocking event and leads the team back to Annie’s inner circle.