Season Finale - Troubled by historical DNA evidence results, Jimmy has to face the fact that Duncan may have been involved in Lizzie Kilmuir's murder, and potentially Sally McColl's as well. A shocked Duncan is brought to the station for questioning, hurt that Perez would even think him capable of murder. However, the detective knows Duncan's lying - perhaps not about the murder, but about something else significant. So when Duncan finally admits he had an affair with Donna, it's not long before a bombshell is dropped.

Perez struggles to deal with what has happened to Tosh as he continues to investigate the murders of Robbie Morton and Michael Thompson, but a shocking discovery finally leads him to the identity of who Thompson was going to testify against.

As the investigation reaches its final stages, Detective Inspector Perez and his team discover the person responsible for the deaths of Robbie Morton and Michael Thompson is closer to home than any of them thought.

Perez and his team are determined to track down the person who helped Michael Thompson's killer on Shetland. But the closer the team get to the truth in both Shetland and Glasgow, the more dangerous it becomes for all of them.

Perez must re-assess the investigation in the aftermath of the attack. The MIT arrives on Shetland and sets its sights on Malone. Meanwhile, Tosh begins to have doubts about Lars.

When a young man disappears on the Aberdeen to Shetland ferry crossing and a small boy ends up in intensive care, DI Jimmy Perez and his team investigate, becoming convinced the two events are connected.

DI Jimmy Perez is convinced that Michael Maguire is somehow implicated in the death of Robbie Morton. But with the investigation seemingly under threat before it's even started, he faces an uphill battle to uncover the truth behind Maguire's silence.

The murder investigation takes Perez and Tosh to Glasgow as they try to uncover the reasons behind Maguire's brutal death and his connection to Robbie Morton. But old ghosts return to haunt Perez as his enemies try to prevent him from getting to the truth.

Detective Inspector Jimmy Perez believes he and his team are finally closing in on the killer as they discover what 17-year-old Catherine Ross was hiding from everyone in the hours before her death.

When Thomas Malone has his murder conviction overturned after 23 years behind bars, DI Perez has to reopen the investigation into the 1994 death of local teenager Lizzie Kilmuir.

Perez is on the trail of an attacker, Tosh investigates an oil company in the hunt for Sally's killer, and DNA testing in the Kilmuir case yields a surprising result.

Perez closes in on Zezi's location at last. But can he reach her before it's too late?

Jimmy questions Donna about the shocking DNA results, Alison arrives in Norway in search of Andreas Hagan, and an unexpected twist leads Perez and Tosh into the murky world of the Norwegian far right.

Ignoring Secret Service warnings, Perez and Tosh track down Mathias Soderland. Back on Shetland, a beach memorial service is held for Sally McColl.

When a prominent and controversial Shetlander is shot dead on their doorstep in broad daylight, Perez rushes back from his mother’s funeral to lead the investigation.

As Perez closes in on the identity of Galbraith’s killer, he struggles with Duncan’s secret, while Donna has one more surprise in store.

Perez issues a warrant for Connor’s arrest and looks for the motive behind his bomb-making. Sandy tries to find out what business William Rodgers had in Shetland.

Old wounds are painfully reopened for the shocked residents of Ravenswick, as Detective Inspector Jimmy Perez and his team look to a past crime to solve the present day murder of a young teenage girl.

A severed hand washes up on a Shetland beach, with further body parts discovered in a holdall that has been dumped at sea. Perez and the team begin a complex murder investigation.

The discovery of Niki’s body intensifies the search for Zezi. Perez feels that time is running out. A desperate Olivia tries to get information from Jamie Hayes.

After the shocking events of the previous night, Perez must piece together what happened before a rampaging and vengeful Creggan finds his target.

Facing a dead end in the hunt for Galbraith’s killer, Tosh leads Perez to the remote island of Fetlar. Donna asks Duncan for one last favour.

DI Perez investigates the disappearance of a vulnerable young man, whose family are new to Shetland. Has whatever they are running from come back to haunt them?

Mounting evidence pushes Perez and the team to revise their view of Connor Cairns. Is he a vulnerable missing person or a killer on the run?

Perez and his team face a race against time to prevent disaster striking Lerwick. With nowhere left to run, an increasingly desperate killer looks to make a devastating political. As the investigation draws to a close, Perez faces a life-changing decision.