London, 1853. On the banks of the Thames, renowned American entrepreneur Colonel Samuel Colt sets up a state-of-the-art weapons factory, capable of turning out his patented revolvers in their thousands. Before long, he is barging his way into the grandest halls of the Empire, determined to win the custom of the British government. When Edward Lowry is hired as Colt’s secretary, he is amazed by his good luck. But then he starts an affair with a girl from the factory floor, and soon realises that things at the pistol works are not what they seem. Among Colt’s machine operators are a desperate gang from the Devil’s Acre, one of the worst slums in the city; and cheap labour has a high price. As guns start to go missing, it becomes clear that there are many with scores to settle and murder in mind.