London, 1758: Beatrice Scarlet has returned to London and found work at St Mary Magdalene's Refuge for fallen women. Beatrice enjoys the work and her apothecary skills are much needed. But when twelve girls sent to a factory in Clerkenwell disappear, Beatrice is uneasy. Their would-be benefactor claims they were witches, sacrificed by Satan for his demonic misdeeds. But Beatrice is sure something much darker than witchcraft is at play...