 So they're walking. He's done it, and if they're walking, they're talking. Oh, talking in rather a different way, no doubt. I knew Niels would never let go, as long as he could just get through the first few minutes, just out of curiosity. Now, and now we'll turn into two or three, perhaps. The first thing they ever did when they met was to go for a walk together at Göttingen after that lecture that Niels gave. He immediately went to look for the presumptuous young man who'd queried his mathematics and swept him off for a tramp in the country, strolling along the forest paths at his fielder, going down to the beach with the children, and Heisenberg was holding Christian's hand. Yes, and in Copenhagen, every night after dinner, they would go for a walk and take the children out to the park and down to the harbour. Oh, Christian loved the harbour. Walk and talk long, long before walls had ears. A lot of this century's physics they did in the open air, but this time in 1941, their walk takes a different course. Ten minutes after they'd set out, they're back. Well, I've scarcely had the table cleared when there's Niels standing alone in the doorway. I can see up how upset he is. He can't look me in the eye. I know something terribly bad has happened. My worst nightmare come true.