When Marie, the spoiled daughter of a sugar baron living in 19th-century Montreal, meets the brilliant Sadie, the two are immediately inseparable. Marie has bubbly charm and sees the pleasure of the world, whereas Sadie's obsession with darkness is all-consuming. Class and circumstance lead them down different paths, while each woman plays an unexpected role in the events that upend their city.

When We Lost Our Heads is a story that explores gender, power, sex, desire, class and status.

Heather O'Neill is a writer and author from Montreal. O'Neill's debut novel, Lullabies for Little Criminals, was a finalist for a Governor General's Literary Award and won Canada Reads 2007. The Montreal-based writer was the first back-to-back finalist for the Scotiabank Giller Prize: her novel The Girl Who Was Saturday Night was a finalist in 2014 and her short story collection Daydreams of Angels was a finalist in 2015. Her latest books are the novel The Lonely Hearts Hotel and the nonfiction book Wisdom in Nonsense.