Christmas Eve, 1940. On the Pelican Road, an isolated stretch of railway between Meridian, Mississippi and New Orleans, two trains travel toward one another through the snow. A.P. Dunn, engineer aboard the 4512, a southbound freight, can remember every detail of the last trip he made in the snow, in 1923. What he can't recall are the events of a few hours ago: where he ate his breakfast, how he got the troublesome gash. On the northbound Silver Star,...