National Security Agency translator Charles Griffin is puzzled by repeated appearances of the word beda (meaning "disaster") in radio transmissions from the Soviet Union. In Leningrad, Admiral Evgenie Komkov is similarly bewildered by orders to prepare for an evacuation of his city in the unlikely event of its being flooded by the river Neva. A Mexican astronomer sights a stray comet he assumes to be Halley's gone astrayand estimates that it will soon collide with the moon, setting off massive tidal waves across the globe. As America gets ready for the catastrophe, and as U.S. space shuttle commander Lee Carradine prepares to use laser technology to fend off the collision, it turns out that the comet isn't Halley's after allit's Moscow's. Robinson's second novel (after An American in Leningrad is equally a delight and a disappointment. His formidable narrative talent is in full force here, but a strand of childish idealism pervades the novel (as when one character exults in a 90-cent subway ride as the best deal in New York), and a primer-level style of dialogue renders some of his observations on Russia and science borderline pastiche. With a more mature vision, Robinson would be a talent to be reckoned with; in this novel, however, he offers us only diversion.