The genre-bending novel, part love story, part spy thriller, follows Tom (Cumberbatch), a seemingly-ordinary man who suffers from a very rare condition called anageria, which has kept him alive for centuries. Throughout history, Tom and men and women like him, have been feared, misunderstood and persecuted. Their lives are one of perpetual loss, as they see family, friends, lovers and children die before them. To survive, those with anageria have formed a secret society to protect their own, but also to enforce strict rules of behavior. The first rule, and the one Tom threatens to break: never fall in love.