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. Following their visit, Jane overhears her father reassuring his pushiest creditor that the Russians have pledged diamonds to support his publishing venture, the Juvenile Library, relieving his financial burden. But when Godwin is told the man who promised the diamonds was pulled from the River Thames, his dire 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.

London, 1814: Mary Godwin and her stepsister, Jane Clairmont, possess quick minds bolstered by an unconventional upbringing. Though quieter and more reserved than the boisterous Jane, Mary’s imagination is keen, and she longs for real-world adventures. One evening, an opportunity arrives in the form of a dinner guest. At 21, Percy Bysshe Shelley is already a renowned poet and radical. When Mary comes downstairs in search of a book after the party has broken up, she finds instead a man face down on the floor --- with a knife in his back. Mary, Jane and Shelley are all drawn to learn the truth behind the tragedy, especially as each discovery seems to hint at a tangled web that includes many in Shelley’s closest circle. But as the attraction between Mary and the married poet intensifies, it sparks a rivalry between the sisters.