Shetland's season 8 twist is far smarter and more sinister than it first appeared

O'Donnell also echoed that sentiment in another interview a few days before the new chapter debuted.

"They're brought in something totally different to really shake everybody up," she said. "And as actors, it was so exciting for us because it allows us to try different things. Risk brings out a different side in all of us."

And they weren't wrong.

When season 8 finally premiered after months of anticipation about the impact of Henshall's exit on the show, Shetland had undoubtedly entered a new era, something we noted in our review. Ruth's introduction had changed things, much of which stemmed from her dynamic with Tosh, which is markedly different from how the character interacted with Perez, and there's also Ruth's own backstory, which is slowly being unravelled as we learn more about her.

Then there's the case itself, which revolves around the aforementioned runaway witness Ellen Quinn. Following the shooting in London, she fled back to Scotland, but with two gun-toting gangsters trailing her, it was only a matter of time before she met her maker – and at the end of the first episode, she was found dead.

But it wasn't Howell and Nowak who had murdered her, but someone from Shetland itself.

"You've got yourself a homegrown killer running around," the former said to Ruth in the interview room, an eerie score heightening his observation.

It's an infinitely more sinister outcome than Ellen dying at the hands of the two out-of-towners who she had a tenuous connection to. Instead, she was murdered by someone that she had a relationship with, whether a family member, a friend, or another from the local community.

She could have been forced inside the vehicle on that dark and lonely road on which we last left her after she escaped Howell and Nowak, but there's also the possibility that she willingly climbed inside after recognising a familiar face, one she trusts, which makes this development significantly more unsettling, and cleverly takes the investigation in a whole new direction.

And that wasn't the only piece of information we learned.

Tosh's digging into the mysterious sheep killings plaguing farmer Agnes Moffatt, the woman who was held hostage by Howell, was essentially paused when Ruth arrived on the scene as they raced against the clock to locate Ellen. But during the post mortem, it emerged that the two cases are linked after a tattoo matching the symbol found on the animal carcasses was also located on Ellen's body, blowing this mystery wide open.

While Howell and Nowak blew in like a tornado and caused sizeable damage during their short stay in Shetland, including the death of humble shopkeeper Maura Watt, the truth looks set to be far more destabilising for the local community.

That twist, engineered brilliantly by writers Paul Logue, Denise Paul and Vivienne Harvey, not only intensifies that sense of creeping dread, but it's also very much in keeping with the tone of the series, and taps into what has kept people tuning in since 2013.

Read more:

• Shetland star on season 8: 'It was always going to be really different'
• Shetland season 8 episode 2: What does Amma's cigarette mean?

Ruth's arrival, while bringing something new to the table, initially looked like it would be a fairly mundane, cut and dry affair, as expressed by one RadioTimes.com reader who bemoaned the "stereotypical villains". But that all looks set to change moving forward.

Perez is now out of the picture, but one man does not maketh this TV show. This is still the Shetland that people know and love.

Shetland season 8 airs on Wednesdays at 9pm on BBC One and iPlayer. Ann Cleeves's Shetland novels are available to buy now. Check out more of our Drama coverage or visit our TV Guide and Streaming Guide to find out what's on.

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