In 1814, Regency-era London, Mary Wollstonecraft-Godwin is a 16 years old aspiring writer who works in the bookshop of her renowned father writer William Godwin, married in second terms after the passing of his first wife, philosopher Mary Wollstonecraft, with the too married by second time Mary Jane Clairmont, where Mary Jane's daughter of her first marriage Claire turns in a close and lovely stepsister for Mary. When Mary and Claire travel at the house of one of William's friends in Scotland, Mary meets the 21 years old poet Percy Bysshe Shelley, rising instantly a love interest between them. Returning to London little time later, Mary unexpectedly meets Percy again when he appears at her house in order to ask William to take him on as an apprentice. Fascinated by Percy, Mary begins a bohemian and torrid relationship with him despite the opposition of her father and her stepmother, especially after they discover that Percy is married with a little daughter whom he supports but he loves no longer. Determined to be free and live on her own terms, Mary flees with Percy to live together accompanied by Claire, who wants to get far from her abusive mother. Their initial happiness turns to tragedy due to the debts and poverty, in addition to the terrible loss of Mary and Percy's daughter, who dies only a few months after to born. Broken by suffering and pain, as well as a season living with the rich, eccentric and hedonist Lord Byron and doctor John Polidori, Mary turns into a shadowy being, becoming more and more obsessed with the idea of resurrecting the dead, while Claire lives a stormy and painful romance with the own Byron. All these events will lead Mary, motivated by a Lord Byron's bet about who can write the scariest horror novel, to find her own voice and exorcise her innermost demons by writing "Frankenstein; or The Modern Prometheus". But when prejudices of these times cause the novel to be attributed to Percy Shelley, it forces Mary to fight by claiming the novel as her own to prove that a woman can be the writer as she is.