Walter Alvarez and his team made one of the most astonishing scientific discoveries of the twentieth century--that an asteroid smashed into the earth 65 million years ago, exterminating the dinosaurs. Alvarez had the first glimmer of that amazing insight when he noticed something odd in a rock outcrop in central Italy. Alvarez now returns to that rich terrain, this time to take the reader on an excavation of the earth's distant past. We encounter...