"Reaping down upon the underworld to smash ganglands comes a friend of the unfortunate an enemy of criminals, the mysterious all powerful character who is a problem to the police. A crusader for law, in reality Dan Garrett a rookie patrolman loved by everyone but suspected by none of being the Blue Beetle. As the Blue beetle he hides behind a strange mask and a suit of impenetrable blue chain armour flexible as silk but stronger than steel."

Throughout the country foreign spies and saboteurs are busy trying to prevent the shipment of war munitions to countries with whom their native country is at war. Near York city is located Explosives Incorporated, one of the largest manufacturers of munitions in the country. Every night trainloads of munitions leave their factory for some secret destination.