Mark Lewis Jones and Nia Roberts have joined the cast of upcoming S4C/Sundance Now anthology series “Still Waters” (“Y Golau:Dŵr” in Welsh).

It is the second instalment of the Welsh psychological thriller, which starred Sian Reese-Williams, following “The Light In The Hall” (“Y Golau”).

Reese-Williams (“Wolf”) returns for the second chapter of the six-episode season, which will be filmed in both English and Welsh. She will also be joined by Robert Glenister (“Spooks”), Tom Rhys Harries (“White Lines”) and Maeve Courtier-Lilley (“The Red King”).

Written and created by Regina Moriarty (“Murdered By My Boyfriend”), the new season picks up two years after the first, with Caryl Huws (Reese-Williams) still living in Llanemlyn. But she’s decided to start a new life, retraining as a journalist.

Her first story is one that immediately leads her into a mystery. Fascinated with the newly announced expansion of the local reservoir, she stumbles across an old case,...