The hard problem that Alice chose was the rising incidence of childhood cancers. And when her carbon-copied questionnaire started to come back, one thing and one thing only jumped out with the statistical clarity of a kind that most scientists can only dream of. By a rate of two to one, the children who had died had had mothers who had been X-rayed when pregnant. Now that finding flew in the face of conventional wisdom. Conventional wisdom held that everything was safe up to a point, a threshold. It flew in the face of conventional wisdom, which was huge enthusiasm for the cool new technology of that age, which was the X-ray machine. And it flew in the face of doctors' idea of themselves, which was as people who helped patients, they didn't harm them. Nevertheless, Alice Stewart rushed to publish her preliminary findings in The Lancet in 1956. People got very excited, there was talk of the Nobel Prize, and Alice really was in a big hurry to try to study all the cases of childhood cancer she could find before they disappeared. In fact, she need not have hurried. It was fully 25 years before the British and medical — British and American medical establishments abandoned the practice of X-raying pregnant women.