In 1704, James Lightfoot, ship's surgeon, returns to Edinburgh to further his studies in medicine. Amid crowded streets, narrow closes and high tenements, he encounters hostility and distrust as he is suspected of being a spy.
His friend, merchant and burgess Andrew Lawson, introduces him to the celebrated physician Archibald Pitcairne, who becomes his mentor. James works tirelessly to aid the sick and poor of the burgh. His efforts are troubled by an encounter with an old adversary – a sea captain who has avoided charges of piracy.
Andrew is sent on a mission to Slains Castle in Aberdeenshire to act as a guide to an agent from France, who is seeking to establish Scottish Jacobites' readiness for a rising. James's loyalties are tested when he becomes unwillingly involved with the Jacobite conspirators. There is still one more emotional battle left to fight; his affection for Louise, whom he fares may make an unfortunate marriage.