Joe Dunthorne had always wanted to write about his great-grandfather, Siegfried: an eccentric scientist who invented radioactive toothpaste and a Jewish refugee from the Nazis who returned to Germany under cover of the Berlin Olympics to pull off a heist on his own home. The only problem was that Siegfried had already written the book of his life – an unpublished, two-thousand page memoir so dry and rambling that none of his living descendants had managed to read it. And, as it turned out when Joe finally read the manuscript himself, it told a very different story from the one he thought he knew. Thus begins a mystery which stretches across the twentieth century and around the world, from Berlin to Ankara, New York, Glasgow and eventually London – a mystery about the production of something much more sinister than toothpaste.