Tom Mathias relocates to Aberystwyth, leaving his past in London behind. Although he is a gifted detective, he is also a man with personal struggles. His expertise lies in understanding that solving a crime depends more on the perspective you take rather than the location you search. Set against the backdrop of the coastal sand dunes and the rugged hinterland, Y Gwyll presents four unique, two-hour narratives that are both deeply rooted in their setting and resonate with universal themes.