Cap and Bucky are on a Japanese island that has been overrun, the Americans are plagued with strange explosions seemingly from nowhere. Professor Rudo has developed a tactical nuclear weapon which he calls "atom water" which detonates upon evaporation from the sun's rays. His men capture Cap and Bucky and leave them tied up outside surrounded by vials of the stuff. Bucky burns through the rope with a magnifying glass and Cap tosses a vial into Rudo's lab. After Rudo executes his own men so that they can tell no tales he retreats to his lab just as the sun evaporates his invention and the lab blows up in his face. Cap takes a sample back to a general, but the general tells him the Americans are miles ahead and have already developed an atomic bomb which will win the war overnight.