Margaret Prior is a prison visitor in the 1870s. Set in and around Milbank, one of London's most notorious gaols for women, the story is both a both a ghost story and an intriguing literary mystery tale.

'There came the splash of water and the rub of heels as Mrs Barber stepped into the tub. After that there was a silence, broken only by the occasional echoey plink of drips from the tap...'Frances had been picturing her lodgers in purely mercenary terms - as something like two great waddling shillings. But this, she thought, was what it really meant to have paying guests: this odd, unintimate proximity, this rather peeled-back moment, where the only thing between herself and a naked Mrs Barber was a few feet of kitchen and a thin scullery door. An image sprang into her head: that round flesh,...