Part one of two. For years, Welsh actor Sheen has been haunted by a story he discovered online about a little-known farming consultant Douglas Gowan, who claimed the people of south Wales had been poisoned by decades of toxic chemical dumping. Teaming up with environmental journalists Dan Ashby and Lucy Taylor, Michael digs into Douglas's archive of evidence, beginning at Brofiscin Quarry near Cardiff, meeting residents who played near the site as children