In 1931, Herbert O. Yardley published a tell-all book about his experiences leading a covert government agency called the Cipher Bureau

Herbert O. Yardley was being followed. He knew it, as much as he knew something was off when a beautiful woman struck up a conversation with him at an illegal speakeasy in New York City in 1929. “Her friendliness was a bit forced,” he later recalled. “It did not seem reasonable for one of her beauty and charm to possess such warmth for a bald-headed man.” The drinks flowed liberally as Yardley sipped straight whiskey, only to let it run slowly through his lips into the ginger ale cup used as his chaser. The woman removed a compact mirror from her purse and disappeared into the ladies’ room. Yardley wasted no time in searching the purse but found nothing except $15, a key and two or three handkerchiefs.

At the end of the night, after Yardley helped the stranger home in a taxi, he waited until she fell asleep, then searched her apartment. In a dresser drawer, he found a typewritten note: “Have tried to reach you all day by telephone. See mutual friend at first opportunity. Important you get us information at once.” The cryptologist covered the woman with a blanket and quietly let himself out. Once again, he’d avoided falling into a spy’s trap. Even so, his days as the head of the top-secret Black Chamberagency were numbered.

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