The chapter opens by introducing Frederick Lindemann, Churchill’s scientific adviser, whose abrasive manner, eccentric habits, and immense influence made him both useful and resented inside government. Churchill valued Lindemann because he could reduce complicated technical questions to practical conclusions, and the prime minister had already made science and statistics central to Britain’s war effort.

Against this background, Dr. R. V. Jones brought Lindemann a troubling theory. Drawing on a deciphered Luftwaffe message mentioning “Knickebein,” earlier evidence from a crashed bomber, and prisoner conversations, Jones argued that Germany might be using long-range radio beams to guide bombers precisely to targets in Britain. Lindemann initially rejected the idea because accepted physics held that such beams could not travel that far in a useful way, so Jones left discouraged but determined to gather stronger proof.

While Jones pursued the matter, Churchill flew again to France for what became his last face-to-face meeting with French leaders. At Tours he found the situation bleak: the airfield had been bombed, French officials were resigned, and Reynaud said everything now depended on the United States. Churchill and his party privately concluded there was little more Britain could do, and Beaverbrook urged Churchill not to promise more RAF squadrons, so the delegation returned home without changing France’s course.

Jones then strengthened his case. He obtained expert calculations from Thomas Eckersley showing that a narrow beam might follow the earth’s curvature, arranged prisoner questioning through Group Captain Felkin, and learned that downed German crews believed the RAF would never find the relevant equipment. When Jones reviewed a captured bomber’s blind-landing receiver, an engineer noted that it was far more sensitive than normal, which suggested it could receive a long-range guidance beam. Faced with this evidence, Lindemann accepted that the Luftwaffe might possess a dangerous targeting system capable of placing bombers within a few hundred yards of a target.

Lindemann immediately warned Churchill, urging rapid investigation so Britain could identify the wavelength and devise countermeasures. Churchill treated the news as a serious threat and pressed Air Ministry chief Archibald Sinclair to examine it. At the same time, the Churchills moved from Admiralty House into No. 10 Downing Street, bringing their domestic life into the center of wartime government just as danger intensified. Late on June 15, Churchill also sent Roosevelt a desperate telegram warning that France might soon collapse, that Britain could be left alone, and that American destroyers and a stronger commitment were a matter of life and death.