In Tiger Bay the docklands of Cardiff rough-and-tumble street urchin Gillie witnesses the brutal killing of a young woman at the hands of visiting Polish sailor Korchinsky. Instead of reporting the crime to the authorities Gillie merely pockets a prize for herself — Korchinsky's shiny black revolver — and flees the scene. When Detective Graham discovers that Gillie has the murder weapon the fiery young girl weaves a web of lies to throw him off course.