She is young, rebellious and ready to overcome all the constraints and conventions of her time: the fate of 16-year-old Mary (Elle Fanning) lead her in 1814 together with the famous romantic poet Percy Shelley (Douglas Booth), who like Mary himself prescribed his life to literature. Despite all opennes and tolereance, the love of the young couple is put to a test again and again. When the poet Lord Byron (Tom Sturridge) challenges Mary Shelley to a literary competition, she invents the most famous literary creature in world history: Frankenstein's Monster!