It’s time for a history lesson. In 1815, Mount Tambora, a composite volcano on the island of Sumbawa, Indonesia, reached a cataclysmic eruption that killed scores of people with its eruptive fallout and tsunamis. It also threw the Earth’s seasons out of whack, creating a long-term negative effect on the global climate.

North Americans and Europeans were acutely affected, and livestock deaths resulted in the worst famine of the 19th century. 1815 became known as The Year Without a Summer, the Poverty Year, and, the ever popular, and Eighteen Hundred and Froze to Death.

1815 was also the year that Mary Shelley had planned to spend the summer of 1815 in a cabin on Lake Geneva with her husband, Percy, and close friend, Lord Byron –  every English major’s fantasy sleepover.  But because of the fluke in weather, the party was forced to spend the entire summer in doors, ultimately leading to the creation of Frankenstein, one of the most heralded science fiction stories ever written.

Tagging along that summer was Mary’s 18-year-old stepsister who had the hots for Byron. The stepsister pursued Byron relentlessly until he made her pregnant, reasoning, “If a girl of eighteen comes prancing to you at all hours, there is but one way.”

With all four pent up in the cabin, surely tensions were running high, since it was also rumored that Mary’s stepsister had slept with her husband, Percy. So one night, for a distraction, Mary decided to start a ghostwriting competition to see who could devise the scariest story.

Mary Shelley won, of course. And that’s how Frankenstein was conceived.

That it was written in an abnormal spell of cold weather caused by an eruption should not come as a surprise to anyone who’s read Frankenstein. Shelley bases the majority of her story in an icy climate, constructing a narrative of bitter disposition. Who knows if Frankenstein ever would’ve been penned without the eruption of Mt. Tambora and the subsequent nuclear winter? And who knows if some guy was stuck in London Heathrow last weekend, because of the Eyjafjallajökull eruption, writing the next great novel on his iPad?

But Shelley, “inspired by this wind of promise, my day dreams become more fervent and vivid,” was not only trying to win some contest. She was also trying, I think, to distract her lewd stepsister from coming on to both her husband and revered colleague. The steely climate of the novel turns any sense of truth into an interminable nightmare, and what’s scarier than finding your husband in bed with your stepsister?