Book IV opens with a soliloquy by Satan. As he looks from Mt. Niphrates toward Earth, he thinks on all that he has done and the options open to him. He concludes that his only recourse is evil, and from now on, all his efforts will be to, if not destroy, at least divide God's kingdom. He will carve out a place where he can reign. As Satan considers these ideas, his face changes, revealing his conflicting emotions. On the sun, Uriel notices these emotions and realizes that the cherub cannot be an angel because the minds of angels are always at peace. Uriel sets off to find Gabriel to inform him of the being in the guise of a cherub.
Satan meanwhile moves toward Earth and Paradise — the Garden of Eden. The Garden is on top of a mountain offering only limited and difficult access. Satan gains access to the Garden by leaping the wall like an animal or thief. Once there, he sits in the Tree of Life in the form of a cormorant, a bird of prey. From this vantage, Satan is impressed with the beauty of Eden and the pure air he breathes. Even so, he begins to plot the destruction of God's new creation. Satan sees Man for the first time as Adam and Eve walk through the Garden. While Satan admires the pair and admits that he could love them, he adds that he, nonetheless, means to destroy them and their peaceful life in Paradise.
Uriel arrives at the gate of Eden to inform Gabriel about the interloper in the form of a cherub. Gabriel responds that no one unauthorized has come to the gate. He adds that if someone has managed to come into the Garden by crossing the wall, he and his assistants will find them by morning.
