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.