In the fields of observation, chance favors only the mind that is prepared.

—LOUIS PASTEUR

The lecture hall in the Kerckhoff Laboratory building at Caltech had rarely been as packed as it was that day in December 1950. Rumor had it that the famous chemist Linus Pauling was about to reveal something truly dramatic—maybe even a solution to one of life’s greatest mysteries. When Pauling finally arrived, one of his research assistants was carrying an object that looked like a large sculpture, covered by a piece of cloth fastened with a string. The lecture itself demonstrated yet again Pauling’s virtuosic command of chemistry, coupled with his exquisite showmanship. After keeping his audience in suspense for a while, Pauling finally used his jackknife to cut the string and, like a magician producing a rabbit out of a hat, unveiled what has become known as the alpha-helix: a three-dimensional stick-and-ball model of the main structural feature of many proteins.

One of the people who soon after heard about Pauling’s pyrotechnical talk, even though at the time he was thousands of miles away in Geneva, Switzerland, was James Watson, who only three years later would discover (with Francis Crick) the structure of DNA. Watson was visiting the Swiss molecular biologist Jean Weigle, who happened to be just back from spending a winter at Caltech. Even though Weigle could not quite judge the correctness of Pauling’s multicolored wooden model, his report on the dazzling lecture was sufficient to intrigue and embolden Watson. We shall return to that gripping story later in the chapter.