London, 1781. Harriet Westerman waits for news of her husband, gravely injured at sea. The city is seething with rumour and conspiracy, and as London's high society enjoys its privileges spies pass its secrets to the French. After a body is dragged out of the Thames, reclusive anatomist Gabriel Crowther is persuaded to advise on the man's death. Despite accusations that she takes an unnatural interest in murder, Harriet joins him. They follow a trail of secrecy to the opera house where the dead man worked, and where new celebrity surrounds two singers. Behind the scenes, though, a much darker plot is being played out which will lead them into great danger.