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.

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 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.

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

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.

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.

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 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.

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?

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.

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 Calder and Tosh close in on the motive for Eadie’s murder, the pool of suspects narrows.

The hunt is on for Sandy's attacker, before a shocking confession causes tensions to boil over and some Islanders take justice into their own hands.

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.

Perez tries to get the measure of Lloyd. Evidence emerges of another bombmaker. The net closes in around Martin. Sandy uncovers Connor’s interest in a piece of local history.

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

Elderly Shetlander Mima Wilson is found murdered on the archaeological site in the grounds of her croft. Detective Inspector Jimmy Perez and his team investigate. Can Perez unravel the family feuds and secrets that emerge and restore the security of his beloved Shetland Islands?

Events in Lunniswick turn violent as holidaymakers Chris and Hayley risk it all to clear their debts. A paranoid Stevie wants Amy all to herself.

In the aftermath of the fire, Tosh and Calder struggle to get answers from an unreliable suspect. A historic grudge from Eadie’s time as a social worker comes to light.

With two murders and no strong leads, can Detective Inspector Perez and his team apprehend the suspect before crowds descend on the Shetland Islands for Up Helly Aa, the biggest fire festival in Europe?

While Calder pressures Louden for help and Tosh investigates Robert Tulloch, Stevie’s battle to keep her sister turns desperate.

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.

Perez returns to his childhood home after the murder of a scientist on the beautiful island of Fair Isle. Tensions run high as a storm on the mainland forces Perez to work in isolation - and compels all of the suspects to remain together under one roof.

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.

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.

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.

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

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.

Tosh finally confronts Billy about his relationship with Robert Tulloch. Fuelled by guilt over Louden, Calder goes after the people responsible.

Time is running out for Detective Inspector Perez as prime suspect Peter Latimer lies critically ill in hospital. Was the fire a drunken accident, or was Peter Latimer the second victim of a murderer still free on Fair Isle?

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?

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