The Wonderful Visit

1. Temptation and the Fall are recurrent themes in the fiction of C. S. Lewis. Demonic temptation is a pervasive theme in The Screwtape Letters. Satanic Temptation and a Fall averted is a pervasive theme of Perelandra. The Lion, the Witch, and the Wardrobe narrates the temptation, downfall, and redemption of Edmund. The Voyage of the Dawn Treader narrates the temptation, downfall, and redemption of Eustace. In The Magicians Nephew, Lewis synchronizes creation with The fall when Jadis invades Narnia at the moment of creation. The same novel narrates the temptation of Digory in an Edenic/Hesperidian garden, only he successfully resists the temptation. For whatever reason, Lewis seems to be fascinated with these themes. 

2. There's a related, potential theme in Out of the Silent Planet, only Lewis doesn't develop it in that direction. Mars underwent Satanic attack which left it physically damaged, but the three intelligent species remain unfallen. Ransom, a fallen agent, is interjected into that world. That generates contact between unfallen agents and a fallen agent. Yet Ransom, though fallen agent, is benign. He's not a malevolent agent like Jadis, or the Un-man in Perelandra. 

Even so, this raises an interesting idea, although it's not developed in the novel. Although Ransom has no malicious intentions, yet because he is fallen, he can inadvertently seed the unfallen species with evil notions. He's not wicked, but he's like a soldier fresh from the war zone, where you have to watch your back all the time. The kind of precautions and suspicions necessary to survive in a fallen world are foreign to the agents of an unfallen world. Simply by talking about his own experience, by comparing and contrasting his world with the their world, he can unwittingly plant sinister ideas in their imagination that never occurred to them. Like a species with no resistance, much less immunity, to exotic diseases, a well-meaning fallen agent might infect unfallen agents. His presence could prove contagious even though he's not a tempter. That's assuming the aliens, while sinless, are not impeccable.  

3. However, we can also develop the same idea in reverse: the effect of interjecting an unfallen agent into a fallen world. What would be the reaction? John Ruskin once remarked that if an angel was spotted in England, he'd be shot on sight. That prompted H. G. Wells to write The Wonderful Visit. Since Wells was an atheist, and the novel is social satire, the protagonist is not a conventional angel by orthodox standards. Rather, he represents a truly innocent, guileless being. He has no understanding of humans and they have no understanding of him. He provokes hostility by compassionate but clueless actions like freeing farm animals. Eventually, he returns to wherever he came from because his presence is intolerable. 

Although that's fictional, it has realistic analogies. Take the persecution of Christians. The virtuous are hated in a world where the normal is vice. The supreme example is the homicidal hostility to Jesus. Darkness fears and despises the light.