Dr Will Raven is a man seldom shocked by human remains, but even he is disturbed a package washed up at the Port of Leith. Stranger still, a man Raven detests is pleading for his help to escape the hangman.

Sarah Fisher has set her sights on learning to practise medicine, despite the dissuasions of her friends and family. Raven's efforts to prove his former adversary's innocence are failing and he desperately needs Sarah's help. 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.