The beginning of the story was strangely familiar, like the opening scene in a shopworn police procedural: A woman runs screaming down a street in Oak Beach, a secluded gated community on Long Island’s South Shore, only to vanish, it seems, into thin air. It was almost dawn on May 1, 2010. Hours earlier, Shannan Gilbert traveled from New Jersey to see a man who had hired her as an escort from a Craigslist ad. By the time the police arrived, she was gone. They talked to the neighbors, the john and her driver and came up with nothing. A few days later, they ordered a flyover of the area and, again, saw no sign of her. Then they essentially threw up their hands. She went into the ocean, they decided, either hysterical or on drugs. None of this made the news, not at first. A missing sex worker rarely does. Not even when another woman advertising on Craigslist, Megan Waterman, was reported missing a month later. This was, quite obviously, a serial-killer case. The only person not sayi...