Michael Harvey’s sequel to THE THIRD RAIL is WE ALL FALL DOWN, in which PI Michael Kelly wears out a great deal of shoe leather trying to save the citizens of Chicago. An unidentified perpetrator may have released a biological weapon in the city’s subway system. When people begin to sicken and die, a highly trained team of brilliant scientists is called in to identify the substance (is it a strain of anthrax?) and try to find a way to contain it. Kelly is a student of Thucydides, who wrote eloquently about the Plague of Athens in his classic work, “History of the Peloponnesian War.” Kelly wonders whether, twenty-four hundred years later, a modern, man-made plague will decimate Chicago.