Captivated by books and stories, Rose dreams of a life away from the confines of the Sunnyside Care Home she works in, until elderly resident Charlotte Favell offers an unexpected glimpse of enchantment. She keeps an aged stack of letters about the Cottingley Fairies, the photographs made famous by Arthur Conan Doyle, but later dismissed as a hoax. The letters insist there is proof that the fairies existed. Rose is eager to learn more, but Charlotte allows her to read only a piece at a time, drawing Rose into her web.

As the letters’ content grows more menacing, Rose discovers she is unexpectedly pregnant, and feels another door to the future has slammed. Her obsession with what really happened in Cottingley all those years ago spirals; as inexplicable events occur inside her home, she begins to entertain dark thoughts about her baby and its origins.