Sarah Lancashire (Happy Valley) stars as Polly Bevan, a devoted mother and loyal wife to a local politician (Mark Lewis Jones, Keeping Faith). But when a construction site collapses and kills a group of teenagers, their daughter is the sole survivor. While Polly blames the project leader (Sidse Babett Knudsen, Borgen), others in their Welsh town find fault closer to home. "Magnificent" -Guardian.