1895: London's scared. A killer haunts the city's streets. The poor are hungry; crime bosses are taking control; the police force stretched to breaking point. While the rich turn to Sherlock Holmes, the celebrated private detective rarely visits the densely populated streets of South London, where the crimes are sleazier and the people are poorer. In a dark corner of Southwark, victims turn to a man who despises Holmes, his wealthy clientele and his showy forensic approach to crime: Arrowood self-taught psychologist, occasional drunkard and private investigator. When a man mysteriously disappears and Arrowood's best lead is viciously stabbed before his eyes, he and his sidekick Barnett face their toughest quest yet: to capture the head of the most notorious gang in London.

1896: Sherlock Holmes has once again hit the headlines, solving mysteries for the cream of aristocracy. But among the workhouses and pudding shops of South London, private detective William Arrowood is presented with far grittier, more violent and considerably less well-paid cases. Arrowood has no doubt who is the better detective, and when Mr. and Mrs. Barclay engage him to find their estranged daughter, Birdie, he's sure it won't be long before he and his assistant, Barnett, have tracked her down. But this seemingly simple missing-person case soon turns into a murder investigation. Far from the comfort of Baker Street, Arrowood's London is a city of unrelenting cruelty, where evil is waiting to be uncovered.