When Polly burst out of the movie theater into the street, she ran into a scene of complete mayhem. Cabs skidded into one another, scraping sparks and denting bumpers. Pedestrians ran headlong into the roadways, blindly seeking shelter.

Though America was not at war with any nation, every year it seemed another mad scientist with another doomsday plan tried to destroy a major city. Polly remembered the flying Iron Sphere and its mind-control antennae, and then it was Lord Dynamo and his terrible lightning-rod zeppelin. By now the population of Manhattan had learned how to react in an emergency. Air-raid sirens pealed out, and New Yorkers raced for designated civil defense shelters.

Called into position by spotters stationed atop the tallest skyscrapers, military and police battalions hurriedly set up defensive blockades. They prepared their weapons and set up cars and tanks as roadblocks. Piercing spotlights swept the darkening skies, searching for the oncoming threat.

A droning, thunderous rumble echoed through the canyons of the city, sounds reflected by the tall buildings. Policemen and soldiers tilted the barrels of their guns high. Terrified people simply pointed their fingers and stared upward.

Polly peered into the slice of sky visible between buildings and saw an aerial invasion force unlike any she had ever imagined. A swarm of strange flying machines cruised overhead, shaped not like aircraft, but metal humans with legs pressed together and arms outstretched as wings. The giant metal men cruised along under their own power, organized in a tight formation descending over New York.

Polly ducked around the corner of a building as uniformed soldiers ran past, their boots clattering on the wet sidewalk. They held rifles and machine guns ready as if they were charging enemy trenches in the Great War. Fifth Avenue was fast becoming a battle zone.