HE WAS ONE of 750,000 people, give or take, who passed through Grand Central Terminal that day. He worked as an attorney in a high-rise on 42nd Street that had direct access to the station, where trains departed every few minutes to 122 towns in New York and Connecticut. He and his wife ran a small firm, specializing in estate law, on the 47th floor of the building; he spent his hours there helping people negotiate death. At the end of the workday on Friday, February 21, the man made his way to the platforms for the New Haven line, boarded a train, and rode 30 minutes north to a commuter town in Westchester County called New Rochelle. At that moment, there were 34 confirmed cases of Covid-19 in the United States, all of them linked to international travel.