Ollie and Moritz are best friends, but they can never meet. Ollie has a life-threatening allergy to electricity, and Moritz's weak heart requires a pacemaker. If they ever did meet, they could both die. Living as recluses from society, the boys develop a fierce bond through letters that become a lifeline during dark times—as Ollie loses his only friend, Liz, to the normalcy of high school and Moritz deals with a bully set on destroying him. But when Moritz reveals the key to their shared, sinister past that began years ago in a mysterious German laboratory, their friendship faces a test neither one of them expected. Narrated in letter form by Ollie and Moritz—two extraordinary new voices—this story of impossible friendship and hope under strange circumstances blends elements of science fiction with coming of age themes, in a humorous, dark, and ultimately inspiring tale that is completely unforgettable.