Causey, James – “Felony” (1954)
Factory supervisor Vogel (a man lacking empathy for his fellow human beings but adept at logistics and machinery; also a racist) is perturbed by new hire “Amenth” who speaks in broken English – “I am not of the understanding. Experience, no. Aptitude, yes.” Vogel just gets more annoyed and suspicious as Amenth loses his accent remarkably quickly, and reorganizes plans and schematics to be even more efficient than Vogel had made them. He also drops hints about Martians, that they could live on Earth “[u]ntil they’d go mad” and so on, and has samples of weird metal in his home – which Vogel finds when he breaks in to get some answers.
Confrontation ensues when Vogel finds that Amenth has built some sort of helmet. Amenth admits that he is from another dimension, but reveals that there he was not a genius but a “criminal moron” exiled to our world for destroying “one of the singing crystals.” Vogel strongarms the helmet away from him and goes to Amenth’s universe, a sketchily-descrbied place of beauty and flame and crystals.
I’ve complained about the leaps of logic in plenty of other stories already, but this one might take the cake: the natives look horrified and rush him, and so Vogel immediately understands that on this world he is ugly, and if it’s a crime to destroy beauty, it must be a duty to kill ugliness – “On this world, he was ugly-”