This is the second book in C. S. Lewis’ space trilogy. The first book is Out of the Silent Planet.
At the close of the last book, the Oyarsa of Malacandra intimated that Ransom might be part of the siege on our world coming to an end. Ransom received orders to go the Perelandra or Venus. The bent Oyarsa of our world was trying some sort of attack on Perelandra. The bent Oyarsa cannot go past our moons orbit so he was using someone else to do his bidding.
Ransom arrives in a coffin like box au naturale. When he arrives on Perelandra, he discovers it is a neo-Eden complete with neo-Adam and neo-Eve. Venus is an ocean world with mythical creatures roaming the sweet waters. The land masses float much like a raft. There is only one solid land mass on the planet.
Soon after arriving, Ransom meets Tinidril who is the Queen of the World. Unlike the inhabitants of Mars, she is human with green skin. It is explained that after Maledil became human he populated Perelandra with humans. The Venutian “forbidden tree” is that Tinidril and Tor may not sleep on the Fixed Land. You can see how Ransom is being changed. Although he is fallen, he lives on Perelandra with Tinidril in nakedness without lust for several weeks.
Then the Temptor comes in the form of Professor Weston, one of Ransom’s abductors in the last book. Weston claims that he has been a changed man; however as time progresses Ransom realizes that Weston has become demon possessed. Ransom’s mission is clear; he is to prevent a Second Fall from happening on this World. Ransom and Weston battle it out for Tinidril’s soul. But Ransom is hard-pressed as Weston’s demonic possession has given him super-human intelligence and brilliance in his arguments.
As Ransom begins to despair that he will win the struggle, he receives instructions in his dream to kill Weston. At first he is reluctant to do so, but after coming upon some creatures that Weston has mutilated, the battle is on. The two fight and fight. I think it went on for days. Weston was near impossible to destroy as he was demon possessed. In the end, Ransom sent him to a literal hell. The victory was not without cost. Ransom was bitten on the heel; and it never heals properly. It was reminiscent of Genesis 3:15 I will put enmity between thee and the woman and between her seed and thy seed, He saw crush thy head, and you shall bruise His heel. Ransom does meet Tor as well as the Oyarsa of Perelandra. He learns where Tor was during Tinidril’s temptation. He also learns what will happen on Perelandra for the next 10,000 and more of the plans to retake Thulcandra. Then Ransom returns home.