Dr Will Raven is a man seldom shocked by human remains, but even he is disturbed by the contents of a package washed up at the Port of Leith. Stranger still, a man Raven has long detested is pleading for his help to escape the hangman. Back in the townhouse of Dr James Simpson, Sarah Fisher has set her sights on learning to practise medicine. Almost everyone seems intent on dissuading her from this ambition, but when word reaches her that a woman has recently obtained a medical degree despite her gender, Sarah decides to seek her out. Raven's efforts to prove his former adversary's innocence are failing and he desperately needs Sarah's help. Putting their feelings for one another aside, their investigations take them to both extremes of Edinburgh's social divide, where they discover that wealth and status cannot alter a fate written in the blood.