Robertson’s serpentine novel isn’t for all readers. Her gothic Georgian mystery is as dense as the slop-ridden alleyways of London in which Harriet Westerman and Gabriel Crowther travel from the Thornleigh estate in Sussex to relocate at Berkeley Square. Harriet must attend to her ailing husband, James. A devastating blow to the head has left his mind struggling to repair itself, and Harriet has little choice but to reside him under the care of a mad-doctor in Highgate.

In 1781, the American war is in danger of being lost. The collusion of the French and an overburdened British naval authority are adding layers of suspicion to an already delicate political climate. When Nathaniel Fitzraven’s body is found below the Black Lyon Stairs, his head lolled to one side, Harriet and Crowther are invited to lead the investigation. Rumors abound that Fitzraven was perhaps working as a spymaster for the Colonies’ European allies.

A strange pair of companions, most recently celebrated for their role in bringing justice to some unfortunates in Sussex, Harriet and Crowther exist far from the Thames' slop and dung houses. There fortune-teller Jocasta Bligh plies her trade, living on air foul with blood and river water. The stink of contagion and of rot forgotten and brooding are a harbinger of something far darker. With the stars in the cards before her, Jocasta sees all sorts of pictures swirling. She doesn’t have good news for shop girl Kate Mitchell, who fortuitously pays the old woman a visit, tasting of salt and gunpowder.

The setting is ripe for complications, secrets, revelations, all leading to a series of violent and tragic outcomes. While the focus of the investigation turns to Fitzraven’s connections to His Majesty’s Theatre in Haymarket, Robertson ties the different strands of the plot together. She brings Harriet and Crowther into the world of music and opera, and to the glorious intrigues of famous castrati Manzerotti and renowned soprano Isabella Marin.

Faced with even more challenges than in Instruments of Darkness, Harriet finds herself overwhelmed by her changed circumstances. Clearly, she has a lot to attend to--most urgently James’ illness, which seems to have overtaken her “like a damp fog.” But there’s also the welfare of her children and the dire warnings of her sister, Rachel Trench, who thinks that ladies of substance should not be recruited to hunt out “mad singers as well as murderers.”

Death reaches out with "his long greasy fingers." Hints of a psychopath preying on young street boys are subtly integrated into Fitzraven’s treachery. Robertson carefully layers her plot, alerting us to what's happening without us missing any obvious clues. As Harriet and Crowther tackle the prickly problem of yet another murder, one character is thought to have committed suicide while Manzerotti and Marin’s voices flow together in a strange alchemy, their singing perhaps holding the key to accusations of plagiarism.

In the doss-houses of Clerkenwell, London thrives on an assortment of rich and poor characters who reveal their true agendas. Good-humored and intelligent, Westerman and Crowther are the perfect provocateurs: no one knows better how the ramifications of a boy's betrayal and the viciousness of a Lord's ambition rest on the delicate spirit of an angel and on the faded glories of Manzerotti’s tender, legendary voice.

A tough read but a rewarding one, Robertson's tale is loaded with connections tied to the malignant and the dangerous. Even her prose--far from fluid, but never awkward--is reminiscent of the novels of the time period as she carefully selects details to reflect an atmosphere of perpetual intrigue and violence.