June 1890. Leeds is close to breaking point. The gas workers are on strike. Supplies are dangerously low. Factories and businesses are closing; the lamps are going unlit at night.

Detective Inspector Tom Harper has more urgent matters on his mind. The beat constable claims eight-year-old Martha Parkinson has disappeared. Her father insists she's visiting an aunt in Halifax - but Harper doesn't believe him. When Col Parkinson is found dead the following morning, the case takes on an increasing desperation.

But then Harper's search for Martha is interrupted by the murder of a replacement gas worker, stabbed to death outside the Town Hall while surrounded by a hostile mob. Pushed to find a quick solution, Harper discovers that there's more to this killing than meets the eye - and that there may be a connection to Martha's disappearance.