Koskinen has returned to earth with a strange new ‘Shield’ – a device which enclosed the wearer in a force screen that absorbed all energies below a certain level.  Light could come through the Shield but no weapon known to man could penetrate it. Koskinen had developed the shield in collaboration with the Martians.  From the moment of his return to earth he was in deadly danger.  His own country sent men to kill him to prevent the Shield from falling into other hands…and soon the whole civilised world was searching for the one man who was armed with the greatest potential military weapon mankind had ever seen.