Victoria Mas’s enthralling and wonderfully imagined first novel is based upon an actual event. Back in the late 19th century, the great gloomy madhouse of La Salpêtrière became an unexpected draw for Parisian society. There were two main attractions, the more outwardly respectable of which were the remarkable public lectures at which Dr Jean-Martin Charcot used hypnosis to present to a riveted audience the spectacle of an attractive and compliant inmate unleashed, under the great physician’s will, into what appeared to be the throes of an orgasm. The second attraction was the Lenten ball.

I’ve been unsuccessfully trying to find out who it was who first dreamed up the grotesque idea of throwing an annual ball for three hundred ‘mad’ women. This was an event at which, magnificently dressed by wealthy Parisians with money to burn, the inmates of an elegantly designed asylum could mingle, dance and even flirt with voyeurs willing to pay handsomely to amuse themselves. The piquancy of the occasion lay in the fact that nobody at this particular event could be entirely sure, behind the masks and disguises, who was ‘mad’ and who was ‘sane’. For the inmates, it was the night when they dreamed of a miraculous reprieve.

The ball scene is reserved for Mas’s suspense-filled climax. The story is about two women drawn together by circumstance and – as it artfully turns out – mutual need. Geneviève, the hospital matron and Charcot’s doughtiest supporter, secretly grieves for a dead sister to whom, night after night, she writes