Young, idealistic, newly qualified Scottish doctor Andrew Manson arrives in Wales and takes his first job in a mining town, and begins to wonder at the persistent cough many of the miners have. When his attempts to prove its cause are thwarted, he moves to London. His new practice does poorly, but when a friend shows him how to make a lucrative practice from rich hypochondriacs, it will take a great shock to show him what the truth of being a doctor really is.