Under the glow of a full moon, a sadistic murder is committed on Nordkoster Island. A young pregnant woman is buried in the sand and slowly drowns as the tide rises. 25 years later, the case remains unsolved. Rookie police officer Olivia Ronning gets assigned to it during training and becomes obsessed when she discovers that her father, who died years prior, worked on the original investigation.

When human remains are found by a highway near London, Cassie and Sunny are called in. Dogged work leads the team to a sixteen-year-old girl who went missing on the eve of the millennium. A close-knit group of old school friends hold the key to what happened. Is one of them capable of murder? Cassie is determined to correct the mistakes made in the original investigation no matter the personal cost

The BAFTA-winning hit series returns, as DCI Cassie Stuart and DI Sunny Khan investigate a cold case with alarming links to the police force. A corpse is discovered in a scrapyard. Four suspects emerge; all have links to the law and attended the same police training course back in 1989. Since then their lives have gone in very different directions. But exactly who is fighting for justice? Can the police force ever really be trusted? And will Cassie...

Follows DI Jimmy Perez and his DS, "Tosh" MacIntosh, as they investigate how the cold case of a teenager's murder is linked to their current investigation of a journalist's murder.

For Aaron Falk, going back home is not going to be easy. After all, with the area facing an extreme drought, everyone is in a constant state of alert. It is against this strange backdrop that Falk stumbles into a mystery that is four decades old. Many years ago, a teenage girl died under mysterious circumstances. And the more that Falk investigates this cold case, the more he realizes that it may have something to do with the town's more recent tragedies....