Shetland

DI Perez and his team must re-open a murder investigation when Shetlander Thomas Malone has his murder conviction overturned after 23 years behind bars. In 1993, teenager Lizzie Kilmuir was strangled to death and Malone was jailed for the crime. Now new DNA evidence has come to light provoking Malone's release, but many islanders still believe him to be guilty, including some officers amongst Perez' own team. Perez talks to retired detective Drew McColl about the case. Drew was the officer who originally convicted Malone and he remains utterly convinced of his guilt even after all these years. But on listening to the original interview tapes from Malone's arrest, Perez isn't so sure.

A traumatised Malone arrives at the station demanding justice after being buried alive and left for dead. He says he doesn't know who's responsible, but Perez suspects he knows more than he's letting on. At oil company Forst Energy, Tosh is given the bare minimum of information about Andreas Hagan. As she leaves, she spots Meg Hamilton who retracts her statement against the company. Tosh suspects Meg has been paid for her silence. Are Forst covering things up to protect Hagan? Did he murder Sally because she was going to expose him?

Whilst Perez questions Donna Killick about the DNA results, Tosh arrives in Norway to track down Andreas Hagan. Is he the mysterious Norwegian seen arguing with Sally McColl the night she died? On Shetland, Perez is frustrated when Donna swears she doesn't know the identity of Alan's real father. Back at the station, McCabe gets news of the Benny Ray attack. Benny is quick to blame Malone but not keen to press charges against him.

The Norwegian secret service warn Perez and Tosh to stay away from Mathias Soderland. They're meddling in an operation they don't understand. But Soderland is their prime suspect for the murder of Sally McColl and they're not going to be bullied into walking away. A deflated Perez returns to Shetland to face some difficult questions, not only from Rhona but also from Duncan who is worried about Cassie spending so much time with Alan Killick.

Jo's attack has affected the team considerably. Sandy, in particular, is struggling with feelings of guilt. Perez needs to keep everyone on track. In light of the assault on Jo, the pressure to re-arrest Malone has never been stronger. But Perez continues to resist - he needs evidence. They've been focusing on the Norwegian element of the case but now they need to open the search back up again.

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.