The true story of the French engineer and inventor who developed a mine detector for the US Army during WWII—and then went on to transform the oil industry. In March 1940, with Europe at war, French army lieutenant Henri-Georges Doll came to the U.S. embassy in Paris to give a deposition. Doll was an artillery commander, a graduate of France's grandes écoles of science, engineering, and service. He had been mobilized to the front at the start of the war, then quickly recalled to Paris to work on a secret device for detecting the deadly land mines being planted by the German army on a vast new scale. But Doll's deposition that day had nothing to do with the war. He had come to testify in a patent lawsuit pending in Houston, Texas. The case was Schlumberger Well Surveying Corporation v. Halliburton Oil Well Cementing Company: it marked one of the first great industrial battles for control of the technology of oil and gas exploration. When the German army marched into Paris three months later, Doll escaped to America, where he developed his new mine detector for the U.S. army, then settled in a small Connecticut town to become one of the most prolific inventors of the twentieth century. His sixth sense for applied science would help create the modern technology of seeing underground using electrical signals and sound waves—technology that would enable the explosive growth of oil production, and of Schlumberger, after the war. This biography tells his remarkable story.