The atmospheric Welsh crime show The Light in the Hall – Y Golau in Welsh – is back for a second season, with episodes in Welsh airing on S4C from 14 September. The Welsh version will have English subtitles. In due course, an English version will be broadcast on Channel 4 in the UK and AMC+ in the United States. Season two will have the title Y Golau: Dŵr, or The Light in the Hall: Still Waters.

This new series will take us back to the fictional town of Llanemlyn, a tiny place somewhere in South West Wales, near Carmarthen. However, there is an entirely new cast ready to ramp up the intrigue in this tight-knit community. Here’s the setup…

Caryl Huws, played by Siân Reese-Williams of Hidden fame, is re-skilling as a journalist after working in her father’s butcher shop. She’s being encouraged by her tutor, Eve Davies (Nia Roberts), to find a story and tell it with passion.

Meanwhile, two important things are going on in Llanemlyn that will affect Caryl and Eve in different ways. You’ll quickly see how intertwined the lives of the main characters are. Firstly, the water company Greenforge wants to build a new dam which will submerge part of the community, and residents are protesting the plans. Secondly, Rhys Owens (Mark Lewis-Jones) has returned to the town to look after his father – after serving over 20 years in prison for murder.

How are these events tied?

Lots and lots of ways, actually.

Rhys did time for killing his cousin Llŷr back in 1995. At this time, the water company was building its first dam in the area and Rhys and Llŷr were planning to blow it up. The explosion killed Llŷr and although Rhys swore he wasn’t there or responsible for it, he was convicted. Some local residents think the trial was fishy.

Llŷr was Eve’s partner when this occurred, and she subsequently had a daughter called Mabli (Maeve Courtier-Lilley). In the present day, Mabli is a key player in the protests against the new dam. Oh, and it gets even more complicated because Eve is the daughter of Robert Davies (Robert Glenister), head of the Greenforge, who is thus Mabli’s grandfather. Basically, Llŷr tried to blow up his father-in-law-to-be’s dam in 1995 and now his daughter is protesting against the new dam and it all feels as though history is repeating itself.

At first, the journalist Caryl doesn’t really pick up on the potency of the story that’s unfolding. However, Mabli is an artist and Caryl’s interest is sparked when she sees one of Mabli’s works – a video installation about her domestic terrorist father, Llŷr. She also bumps into Rhys Owens, who is a quiet, sultry fellow after his years of incarceration. He strikes her as a bit of an enigma and if there was indeed a miscarriage of justice, perhaps Caryl can write about it.

When she starts asking questions, some of the people around Llanemlyn get tetchy. Some of them have secrets. Some of those secrets are very dark, and some of them are rather sordid. Even before the end of episode one, you’ll see that more than one individual wants to get rid of Rhys Owens. Caryl is walking into a web of relationships she knows nothing about, and there’s a spider waiting for her.

The setup sounds very dramatic, but the writers and cast do make Llanemlyn feel like an authentic Welsh village, as do the cinematographers. Valleys and woods, a sprawling reservoir and ancient farmlands fill the backgrounds. The violence of the past hits us in Rhys’s flashbacks, replaced now with brooding, sorrow and thoughts of what might have been. You’ll visit the pub and the chip shop, the town hall, tiny cottages and huge modern mansions. But most of the town seems stuck in the past. There are one or two fiery characters but the tension builds slowly and the atmosphere of the place is part of the pleasure as you follow the mystery.

In that sense, it has many of the same qualities as other Welsh crime dramas such as Hinterland and Hidden. It’s good to see the Welsh culture and geography coming to the fore in crime TV, and the language too. It’s worth noting that Welsh is the most spoken of the surviving Celtic languages, bringing an ancient rhythm to the dialogue that reaches into Britain’s deep, shadowy past.

Y Golau: Dŵr / The Light in the Hall: Still Waters consists of six one-hour episodes. There are several ways to watch S4C outside (and inside) Wales. It is included in the BBC iPlayer, and there is the S4C Clic app for smart TVs, Apple and Android devices. It can also be watched live on the website, although you will have to sign up and log in.

Also see the Irish language crime show Crá and the Scottish Gaelic crime show An t-Eilean.