Edinburgh, 1850. Despite being at the forefront of modern medicine, hordes of patients are dying all across the city, with doctors finding their remedies powerless. But it is not just the deaths that dismay the esteemed Dr James Simpson – a whispering campaign seeks to blame him for the death of a patient in suspicious circumstances. Simpson’s protg Will Raven and former housemaid Sarah Fisher are determined to clear their patron’s name. But with Raven battling against the dark side of his own nature, and Sarah endeavouring to expand her own medical knowledge beyond what society deems acceptable for a woman, the pair struggle to understand the cause of the deaths.