1814, London: Foreign diplomats are descending on London in advance of the Congress of Vienna meetings to formulate a new peace plan for Europe following Napoleon's downfall. Mary and Jane's father, political philosopher William Godwin, is hosting a gathering with an advance party of Russian royal staff. The Russians are enthusiastic followers of Mary's late mother, philosopher and women's rights advocate Mary Wollstonecraft, which leads to a lively dinner discussion.

Following their visit, Jane overhears her father reassuring his pushiest creditor that the Russians have pledged diamonds to support his publishing venture, relieving his financial burden. But when Godwin is told the man who promised the diamonds was pulled from the River Thames, his financial problems are further complicated by the suspicion that the family may have been involved in the murder.

Stepsisters Mary and Jane resolve to find the real killer to clear the family name. Coming to their aid is Godwin's disciple, poet Percy Shelley, who seems increasingly devoted to Mary, despite the fact that he is married. And a young woman Jane befriends turns out to be the mistress of the celebrated poet Lord Byron. As both sisters find themselves dangerously captivated by the poets, their proximity to the truth of the Russian's murder puts them in far greater peril . . .