Tall, dark, elegant and tough, Blackstone grew up in the roughest slums of London. He now rubs shoulders with high society as easily as he moves among the thieves, whores and cut-throats of the nineteenth-century underworld. His dangerous career has made him a crack shot - and given him a taste for good wine and fine women. He is ruthless and courageous, and above all a Bow Street Runner.

Blackstone receives a challenge from the mysterious 'Diddiki' that they will break into the bullion vaults of the Bank of England. Suddenly he is faced with a dilemma: a pretty girl implores him to rescue her 13-year-old brother from the gallows. But will he have time to save both the boy and his own professional reputation? The race against time takes him on a dramatic chase through the twilight world of London's underground waterways.

Blackstone Underground is the fifth Blackstone novel.