The scene returns to Heaven, where God knows immediately that Adam and Eve have eaten from the Tree of Knowledge. Gabriel and the other angels guarding Paradise also know, and they fly back up to Heaven. They report that they did all they could to prevent Satan from re-entering the Garden. God tells them that he allowed it himself without condoning it, and acquits his angels of any guilt. He then sends his Son down to Earth to pass judgment on the couple.
In Paradise, the Son calls to Adam, who comes forth shamefacedly along with Eve. They are embarrassed by their nakedness. Asked if they have eaten from the tree, Adam admits that Eve gave the fruit to him to eat, and Eve blames the serpent for persuading her to take it. The Son first condemns the serpent, whose body Satan possessed to tempt Eve. He ordains that all snakes now must crawl on their bellies, never to carry themselves upright again. The Son decrees that Adam and Eve’s children will bruise the serpent’s head, while serpents will forever bite humans by the heel. As punishment for the couple, Eve and all women to follow will give birth in pain, and must submit to their husbands. Likewise, Adam and all men after him will have to labor to hunt and harvest food in cursed ground. After passing these sentences, the Son returns to Heaven.
Meanwhile in Hell, Sin and Death remain at the gate of Hell where Satan left them. Sensing that Satan has succeeded in his task, they finish the bridge linking Hell to Earth and begin to travel toward Earth to meet him. At the edge of Paradise, Sin and Death meet Satan. They congratulate him for succeeding in his mission and promise him that they will infect the Earth. Death will corrupt all living things, causing them to die, and Sin will corrupt the thoughts and deeds of humankind. They also tell Satan that his success must have allowed them to leave Hell, proving that he has established his control over humankind and Earth. Satan thanks Sin and Death for their praises and urges them to hurry on their way to conquer Earth. Satan believes that he has in fact acquired the special powers Sin and Death spoke of, when in truth God allows them to enter Earth so that the Son can conquer them when he becomes human. Now, Satan goes back down to Hell, where his followers have been eagerly waiting his return. Satan speaks to them from Pandemonium, tells them of his triumph, and expects to hear riotous applause. Instead, he hears hisses signifying scorn for him and his devastating act. The devils have all been transformed into snakes, along with Satan, who did not understand the punishment the Son foretold. A grove of trees appears in Hell, with fruit that turns to ashes as soon as the snakes try to bite it.
Sin and Death arrive on Earth and begin their work. From Heaven, God sees that they have come to Earth and tells his angels that he will allow Sin and Death to stay on Earth until Judgement Day. After then, they must return to Hell and be forever locked up with Satan and the other devils.
God now calls for his angels to alter the universe. They tilt the Earth’s axis or alter the path of the sun (the poem allows for both interpretations). Now humankind will have to endure extreme hot and cold seasons, instead of enjoying the constant temperate climate that existed before Adam and Eve’s fall from God’s grace. Meanwhile, Discord follows Sin to Earth and causes animals to war with each other and with humans too. Seeing these changes, Adam is sorrowful, and laments. He knows that the rest of humankind will suffer because of his disobedience, and wishes that he could bear all of the punishment upon himself. He curses life and wishes that Death would come at once to alleviate his misery. Instead, Eve comes to him. But Adam is angry; he blames and insults Eve’s female nature, wondering why God ever created her. She begs his forgiveness, and pleads with him not to leave her. She reminds him that the snake tricked her, but she fully accepts the blame for sinning against both God and him. She argues that unity and love can save them in a fallen world. She longs for death and suggests that they take their own lives, but Adam forbids it. Eve’s speech affects Adam. He becomes calm, consoling her and sharing responsibility for their fall. They must stop blaming each other, he says. They must live with their mistakes and make the most out of their fallen state. Remembering the prophecy that Eve’s seed would bruise the head of the serpent, he feels that there is hope for humankind and advises that they obey God and implore his mercy and forgiveness. They return to the spot where they were punished. There, they fall to their knees, confess their sins, and ask for forgiveness.
If Book IX presents the climax of Paradise Lost, then Book X presents its resolution, as the punishments that the Son hands out restore some sort of order to the world. Satan and the other supporting characters disappear from the rest of the poem, eliminating the source of human temptation and thus focusing the poem on Adam and Eve’s regret. But Adam and Eve begin to redeem humankind with their repentance at the end of Book X. As a result, these characters will disappear from the story, and humankind’s predicted redemption will take precedence as the story continues, with Adam and Eve learning about their fallen future.