William Dempsey was a wonder among wonders.

By 18, he had risen from a gang of London street rogues to be the personal plaything of the Marquess of Argyll. Maintained in splendour, celebrated at masquerades – with everything he could wish for.

Now all has come crashing down. He is put out in the rain without patronage, his West End apartment, or a place among the ton.

So on a stormy night, he arrives at a house in Southwark. Marathon Moll’s in the Mint – the bawdyhouse he worked in during his ascent and where he earned the name Blue Billy.

But is Marathon Moll’s a place from which to rise again? For there is one in the crowd, who catches his eye. Who takes his hand and promises something better.

Or does Moll’s signify a return to his roots? For one day, a second and very different young man raps on the door. Takes his hand and asks him to return to his past.

To the cat language of vagabonds. The canting dialect of thieves.

To the schemes, and the dreams, of his youth.