Fans across the country are eagerly anticipating the fourth episode of BBC One thriller Vigil tonight, following the huge reveals from last week's instalment.
The show got off to a shocking start when it killed off Line of Duty star Martin Compston, playing submarine staffer Craig Burke, with viewers left to unravel the mystery of who committed the crime.
Detective Amy Silva is hard at work investigating the case, joining the crew of the nuclear vessel and becoming acquainted with the suspects on board.
Those watching at home had many Vigil episode 3 questions, with some wondering what the Vigil theme song is and others wondering where the drama was filmed. Read on for full details on whereabouts in Scotland the series was shot.
Vigil filming locations
Although several of the show's scenes unfold onboard the titular nuclear submarine, filming didn't actually take place on a real submarine – with an elaborate studio set constructed to resemble the real thing.
Speaking exclusively to RadioTimes.com, writer Tom Edge explained, "Tom Sayer the production designer was able to provide blueprints, floor-plans for what the set would be, based off early drafts and the conversations that we had with him about which things felt essential to us.
"And [going onto the set] was a really joyful experience. It did leave us kind of giddy, it was incredible, just lovingly recreated. So the actors when they were working in that space travelling through it, there were no sort of missing fourth walls really, it was that feeling of enclosure and even I felt that on my visits to the set."
The show's lead director James Strong added that it was vital to "create a big enough space to contain the action and be big enough to work in and yet retain all the claustrophobia of a real submarine.
"Creating HMS Vigil was an enormous endeavour, brilliantly carried out by designer Tom Sayer and his team," he said. "It looked incredible, was a great place to shoot and yet always felt utterly real."
More like this
As for the land-based parts of the series, the bulk of filming took place in Glasgow – and throughout the show you might be able to spot some of the city's landmarks including Blythswood Square and the Squinty Bridge (which crosses the River Clyde) as well as streets including Finnieston Street and Hamilton Park Avenue.
- For the latest news and expert tips on getting the best deals this year, take a look at our Black Friday 2021 and Cyber Monday 2021 guides.
The naval base that is key to the series, Dunloch, is not actually a real place – but is based on Faslane, the home of HM Naval Base Clyde on the Gare Loch, although Faslane itself was not actually used in production.
Various other parts of the West of Scotland were used to film these rural scenes, including Cumbrae, a small island off the coast of Largs, and Hunterson a small town in Ayrshire.