Alone in his East London shop, a man known only as Dalton makes living prosthetics: bionic, mechanical limbs, from leather, metal and magic. It's to this little corner of the capital that Finn Croucher, an elite army marksman, travels after an accident leads to his hand being amputated. While Dalton fashions Finn’s new hand and teaches him how to use it, he reveals some secrets long hidden, and he and Finn become lovers. But Finn must return to duty, and a string of letters becomes his only connection to the love he left in London.