Thor is summoned by Odin to Asgard. The All-Father asks Thor to create rain to end the drought plaguing the home of the gods. The Thunder God calls up a major storm and promises to return in a week to end it. He returns to Earth to attend a scientists’ convention where Professor Zaxton is demonstrating an android invented by Dr. Don Blake. Zaxton introduces Thor and has him rip the heavy steel door off of the cabinet to reveal a huge green android, controlled by a remote held by Prof. Zaxton. For the benefit of the audience, at Zaxton’s command, the android solves the world’s most complicated math problem and withstands hammer blows by Thor. Zaxton’s hand slips on the controls however, causing a short circuit that will lead to its internal organs blowing up. Zaxton isn’t worried because the android’s indestructible skin will contain the explosion. The robot corrects him: an explosion will turn his skin to deadly shrapnel. Thor seizes the creature and hurls it into the sky where it explodes harmlessly….
Thor returns to Don Blake’s office and changes back to his alter ego, only to find Professor Zaxton waiting for him. The visitor demonstrates his new duplicating machine creating a second easy chair and a dozen typewriters merely by pointing his device at one. Zaxton demands that Don help him perfect the machine so that he can duplicate human beings, and to force the hero to comply he is holding Jane Foster prisoner elsewhere. Zaxton, jealous of Don’s success, also reveals that he deliberately caused the android to blow up, not realizing he would be in danger too. Don agrees to help and, after many hours of experimentation, pronounces the machine to be perfected. Zaxton takes the duplicator out into the alley to test it by multiplying stray cats, and Don seizes the opportunity to dash back inside and change to Thor. But Zaxton witnesses the transformation (who ever would have thought he would turn around to see where Don was going?) and quickly makes a duplicate of Thor. But the duplicate has the opposite personality, resulting in an evil twin, and for good measure Zaxton also gives the bad one a second hammer. Zaxton plans to destroy the real Thor and rule the world (bwa-ha-ha) but the Thunder God escape through a window. The quick-thinking villain duplicates the office building across the street and Thor crashes into it and the evil twin is on him. Thor calls down lightning to strike the duplicate and hurls his hammer at his stunned foe; Zaxton hurriedly generates another duplicate to receive the blow which vaporizes it. Thor attempts to fly away but Zaxton multiplies airlines to block the sky. The evil twin hurls both his hammers at Thor’s chest but they strike without effect: since the fake is not worthy of Thor’s power, he doesn’t have it. Realizing he’s safe from the duplicate, he smacks it with his hammer so that it disintegrates then heads for Zaxton. The villain quickly makes a copy of himself to confuse Thor but then he stumbles and drops the duplicator over a parapet and his lunge to retrieve it sends him to his death. Thor realizes that the fake Zaxton—a good version—can take the evil one’s place and he rescues Jane Foster from her imprisonment, explaining that Zaxton was temporarily insane. He then returns to Asgard to end the rain.