Book excerpt: Tomie dePaola's glorious paintings are as luminous as the farolitos that light up on the Plaza in Santa Fe for the procession of Las Posadas, the tradition in which Mary and Joseph go from door to door seeking shelter at the inn on Christmas Eve.This year Sister Angie, who is always in charge of the clebration, has to stay home with the flu, and Lupe and Roberto, who are to play Mary and Joseph, get caught in a snowstorm. But a man and a woman no one knows arrive in time to take their place in the procession and then mysteriously disappear at the end before they can be thanked.That night we witness a Christian miracle, for when Sister Angie goes to the cathedral and kneels before the statue of Mary and Jospeh, wet footprints from the snow lead up to the statue.