What happens when two people become so connected that the world outside simply disappears?

June and Jennifer Gibbons were identical twins who grew up in Wales. From childhood they slowly stopped speaking to everyone around them—teachers, family, strangers—until eventually they communicated only with each other. No one else could understand them. They lived inside their own private world, writing stories, creating strange routines, and isolating themselves from society.

As the years passed, their bond became darker and more disturbing. The twins began committing crimes together, including theft and arson, which led to their arrest and confinement inside Broadmoor, one of Britain’s most notorious high-security psychiatric hospitals. There they spent more than a decade, studied by doctors and psychologists who could neve ...