In late Victorian England, private enquiry agents Cyrus Barker and Thomas Llewelyn find themselves in the middle of the deadly chaos when powerful forces align to take over London's criminal underworld.

Private enquiry agent Cyrus Barker, along with his partner Thomas Llewelyn, has a long, accomplished history - he's worked with all aspects of society, from the highest (including the Crown and the government) to the lowest (various forces in London's underworld). He's been the target of murder attempts, character assassination, bombings and attacks upon his closest associates but never has he and his agency partner Thomas Llewelyn faced such destruction and potential disaster.