Plot

Act 1

It is the summer of 1816 - ‘the year without a summer’. Lord Byron and Dr John Polidori, his much maligned personal physician, flee London for the continent to escape the scandal of Byron’s rumoured affair with his half-sister and an ever greater gambling debt.  Claire Clairmont, having slept with Byron before his departure, and holding creative ambitions of her own, persuades her half sister, Mary, to follow him abroad. They are joined by Mary’s lover, Percy Shelly, an up and coming poet in the romantic movement who is also eager to meet the great man.

The two travelling parties awkwardly meet each other at Hotel d’Angleterre on the shores of Lake Geneva where Byron seems more interested in Shelley, and Polidori takes a shine to Mary. Byron invites Shelley, Mary and Claire to his villa - the beautiful Villa Diodati - for dinner. Byron and Shelley discuss some of their past indiscretions and Byron makes a pass at a totally oblivious Shelley. As the rain starts to fall Polidori attempts to help Mary who is struggling back to the Villa but he falls from a wall in the process twisting his ankle. As Mary helps him he admits to her that he’s being paid to keep a diary of the trip. A fierce storm sets in; Claire uses this as an opportunity to propose they stay, which Mary and Shelley agree to. On one particularly stormy night, they take it in turns to read ghost stories, which leads Byron to set the group a challenge: to each write a horror story of their own.  As the various party members retire to bed, Claire and Byron are left alone.

Act 2

Byron and Shelley are setting out to St. Gingolph, on a pilgrimage in the footsteps of Jean-Jacques Rousseau. The pair nearly drown, on account of the continued storm and poor seamanship, but struggle ashore to take lodgings in a nearby inn. Whilst there, Byron attempts to meet his own writing challenge, but fails, only producing a fragement of a story. For the first time he expresses some regret and guilt over his treatment of Claire. Back at the villa Claire, Mary, and Polidori try to bolster each other in their attempts to write.

Upon their return to Villa Diodati, Byron and Shelley debate the role of God in their lives, with Shelley revealing the reasons behind his atheism. Claire makes a startling discovery: she is pregnant by Byron.  She tells him but he reacts with denial. Mary suggests to Claire that the two of them along with Shelley take a trip to Chamonix, in the mountains, to help consider what to do next, and so that Mary might write.

Byron discovers that Polidori has been paid to keep a secret account of his time in Geneva.  Shelley notices Polidori writing about Mary in his diary and confronts him. Feeling slighted, Polidori challenges Shelley to a duel but Byron, reacting angrily to the news, steps in to take Shelley’s place. Polidori calls off the duel and fuelled by resentment is provoked into writing his own story, basing his villainous protagonist on Byron himself: ‘The Vampyre’

During the journey to Chamonix, Mary and Shelley discuss the death of their first child and how, after it initially pushed them apart, they are slowly healing and growing closer.  Claire and Mary talk about the challenges they have faced in a man’s world. While in Chamonix, on waking from a nightmare, Mary begins to write. Born from an obsession with the idea of bringing her dead baby back to life and the science of galvanism the story of ‘Frankenstein’ begins to take shape.

Mary and Shelley tell Claire that they must return to Villa Diodati and confront Byron about arrangements for their unborn child.  Claire alights on the notion of giving it away to Byron and forever leaving his life, on the condition that he raises the child with his name and title.  Mary has mixed emotions regarding this, understanding the logic, but struggling to reconcile the proposal against her own recent bereavement.

On returning to the Villa, Claire comes to the realisation that Byron is a deeply flawed man, who will never love her; and that her baby’s future is more important than her own. 

A short epilogue gives a brief outline of what happens to each of the protagonists, after that fateful summer.