In the winter of 1664-65, a bitter cold descended on London in the days before Christmas. Above the city, an unusually bright comet traced an arc in the sky, exciting much comment and portending "horrible windes and tempests." And in the remote, squalid precinct of St. Giles-in-the-Fields outside the city wall, Goodwoman Phillips was pronounced dead of the plague. Her house was locked up and the phrase "Lord Have Mercy On Us" was painted on the...