Shetland season 6 ending explained: What will happen to Jimmy Perez and Duncan?

The season started off with Jimmy in a dark place, struggling to cope with the death of his mother, whose wake he was attending when he got the call that local hot-shot lawyer, Alex Galbraith, had been murdered in cold blood on his own doorstep.

Throughout the season, Jimmy was in emotional turmoil over several issues, including his father's dementia, his quest to solve the Galbraith's murder, and the return of convicted killer Donna Killick to Shetland (if you're curious about where Shetland is filmed, check out our location guide).

We've unpacked tonight's instalment, breaking down some of the key questions and theories that have come up after the events of the Shetland finale.

Who killed lawyer Alex Galbraith?

In the end, it was the all-important doorbell that gave away the identity of Alex Gabraith's murderer.

Right from the start, the pressure was on for Jimmy to solve the high-profile murder of renowned lawyer Alex Galbraith, who was shot in his own home - while his teenage daughter was on the phone to him at the time of his death.

But Jimmy also had his suspicions that the daughter in question, Merran Galbraith, knew something about the murder that she wasn't letting on.

While on the phone to her father, Merran had heard someone - the murderer - buzz the doorbell three times in quick succession, before her father opened the door and was shot dead. It turned out that she'd recognised the sound of her mother Eve's distinctive, impatient way of ringing the doorbell, often when she'd forgotten her keys (a theory that Jimmy checked by going to the Galbraith residence and buzzing the doorbell three times).

Alex Galbraith's murderer was his own wife, politician Eve. She killed her husband because he intended to tell the police the truth about the death of Marie-Anne, a local young woman who had accidentally died of an overdose at a party, over two decades earlier. The reveal would have ruined the careers of several people who helped cover up her death, including Alex Galbraith - and inadvertently, Eve's own career, too.

The grisly deaths of Sister Carolyn (Shonagh Price) and diver Eamon Gauldie (Thoren Ferguson), who had flown a drone over the Galbraith residence and caught Eve on camera, were both ordered by Eve in order to keep a lid on the secret surrounding Marie-Anne.

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How did Donna Killick set up Duncan and Jimmy?

Season six saw the return of a familiar face: Donna Killick, who (back in season four) was revealed to be a murderer after Jimmy Perez reopened the cold case murder of teenager Lizzie Kilmuir. Donna also had had an extramarital affair with Duncan, and later gave birth to his son.

Early on in season six, she was returned home to Shetland on compassionate grounds, after she was diagnosed with cancer while in prison. Out of guilt, Duncan went to visit her, and she soon began to manipulate him (something Jimmy predicted).

However, it soon became clear (at least to the viewer, if not Duncan) that Donna intended to get her revenge on Duncan, whom she believed "betrayed" her back in the day. She convinced him to help her die by suicide before she could be transferred back to prison, which he did by mixing all her medicine into her mug of hot chocolate for her.

Jimmy arrived at the scene after Donna's death, and convinced Duncan to carry the mug to the kitchen sink, to explain away why his fingerprints were on the side.

That appeared to be the end of it, until it was revealed that Donna had written to her lawyer shortly before her death, swearing that Duncan was pressuring her to die by suicide, even threatening to kill her himself - and that Jimmy Perez was in on it, too.

Distraught and determined to save Jimmy's career, Duncan headed to the police station to confess and tell his side of the story. However, the plan backfired and Jimmy was arrested in the final moments of the episode.

Jimmy and Duncan's fates have been left uncertain, but it seems likely that Shetland cast newcomer Meg Pattison (played by Lucianne McEvoy) will have a key part to play, given that she was Donna's carer - and a potential love interest for Jimmy.

Is DS 'Tosh' McIntosh pregnant?

The one bright spot at the end of the season finale was the reveal that DI Jimmy Perez's loyal, whip-smart second-in-command, Tosh, is pregnant with her first child.

Earlier in the season she had expressed doubt about wanting to become a mother in the near future, preferring to focus solely on her career. However, when she noticed that her sense of smell had become heightened (specifically, her disgust at poor Sandy's ham sandwich), she bought a pregnancy test.

Viewers watched as she checked the result, which confirmed her pregnancy - and her shocked face slowly broke into a grin.

While you wait for Shetland season seven, you can visit our TV Guide to see what’s on tonight.