Gil Cunningham had hoped that the first time he set foot in the brothel on the Drygate it would also be his last, but by the time all was settled he felt quite at home within its artfully painted chambers. The bawdy house, along with the neighbouring property and two more in Strathblane, are all part of a deal offered to Gil and his wife Alys by the forceful Dame Isabella. Her proposal also involves Gil's young ward, and matters are further confused by an outbreak of counterfeit coins in Glasgow, which Gil has been ordered to investigate.

Then Dame Isabella is found dead in strange circumstances, and the more Gil pursues the cause of her death, the more false coins he finds. And then the bawd-mistress, the enigmatic Madam Xanthe, gets involved and rumours circulate that the Devil is abroad in Strathblane. By the time Gil and Alys have untangled matters, some very surprising - and sinister - thing have come to light...