CI Tom Mathias comes to Aberystwyth having abandoned his life in London. He's a brilliant but troubled man. Despite his faults he is an excellent detective, who knows that the key to solving the crime lies not in where you look for truth, but how you look. From the windswept sand dunes of the coastline to the badlands of the hinterland, Y Gwyll is a series of four two-hour stories that are original and local, yet timeless and universal.

Overview from themoviedb.org