Book 1 of Paradise Lost opens in the traditional epic style, with a Homeric invocation to Milton’s Muse. Milton proclaims his lofty poetic purpose: to do the unattempted, to write a great epic of lasting literary importance about the biblical story of the Fall of Man, Adam and Eve's expulsion from Paradise, and the lasting consequences of ‘Mans First Disobedience’ (eating the fruit from the forbidden Tree of Knowledge). The poem’s ultimate ‘Argument’, Milton says, is to justify the prudence of God’s judgement to its readers.

Milton introduces Satan as the seductive agent of Adam’s and Eve’s transgression and as the leader of a host of rebel angels. He recounts the fallen army’s failed rebellion against God, and their subsequent expulsion from Heaven.

The poem then gets to the heart of the action, presenting the reader with an image of Satan and the host of newly fallen angels, writhing in torment and confusion, prostrate on a burning lake in Hell.

Satan gives a rousing speech, rallying his army to resist defeat and vowing terrible vengeance against the ‘Tyranny of Heav’n’. The fallen angels start to rise from their shackles, recovered with Godlike strength by Satan’s stirring proclamation of their sovereignty in Hell. Satan speaks compellingly through his pain and despair. He is charismatic and uses powerful rhetoric. We begin to build up a complex picture of an appealing Satan: Satan as an anti-hero, both tragic and heroic, tortured and proud.

Milton describes the ranks of Satan's army, invoking a long list of monstrous named figures enjoined together under Saran’s command.

Satan begins to lay out his plan: there have been rumours that God intends to create a new world of men; it is there that the fallen angels might guilefully enact their revenge.

The close of Book 1 sees the building of the palace Pandæmonium and the preparations for a council of Hell.

Satan sits kinglike on his royal throne and discusses how, being more united and free in their fall than they ever were in Heaven, the devils can champion their own vision of democracy. He opens the assembly floor to political debate, asking whether they should fight God directly or secretly, with ‘open Warr or covert guile’.

Moloch counsels furious open war. There is nothing to lose, he says.

Belial fears the consequences of battle: being utterly destroyed, or worse, having greater agony inflicted on them by God. The will of the omniscient God is invulnerable, Belial argues. Belial thus counsels inaction, and urges the fallen angels to bear their lot in Hell.

Mammon develops this idea of inaction, advising that they should forge their own kingdom in Hell and enjoy the liberty of a life free from servile subjection to the tyrannous God whose Heaven so often ‘resemble[d] Hell’. A cheer arises from the devils, who receive his argument with applause.

Beelzebub mocks both the possibilities of peace and of war, and puts things into stark perspective: a life in Hell is a life of bondage under divine wrath. He proposes an alternative plan, devised beforehand by Satan himself, to infiltrate and corrupt the prophesied New World of Man. The proposal meets with assent and a brave adventurer is called for to find and infiltrate this new World across the treacherous ‘Abyss’ of space. There is silence. Satan steps up, and is met with praise for his sacrifice.

Satan soars magnificently in ‘solitary flight’ and reaches the blazing gates of Hell, guarded by Sin and Death. Proclaiming himself king of Hell, Death refuses Satan access to the gates, threatening Satan with his fatal dagger. Satan, unafraid, raises his, and Milton prepares his reader for a battle of epic proportions. Rather absurdly, however, Sin prevents the fight by revealing Satan to be her father, and also the incestuous father of her child, Death.

Although commanded by God never to unlock the gates, Sin is ultimately convinced by Satan to do so: Satan promises the terrible pair freedom from their condemnation in Hell, and vows to bring them to Earth, where they might roam freely for prey. Pleased, Sin lets Satan out of Hell’s gates.

Book 3 opens with a second invocation to the poet’s heavenly Muse. Milton asks for divine illumination so that he might ‘see and tell / Of things invisible to mortal sight’, though he is blind.

The poem shifts to Heaven, as God the Father sits on a throne alongside His Son, watching Satan approach Eden. God, who is all-knowing, foresees Satan’s seduction of Adam and Eve: humankind, God knows, will transgress God’s command and fall to sin. From here on, the poem explores some key theological concepts, including the Problem of Evil and Free Will. God insists that, though he has foreknowledge of the fall, humankind has free will; for God created humankind with the faculties of Choice and Reason so that they could have freedom – the freedom to love, to have faith, and to prove their allegiance meaningfully. God tells his Son that He cannot be blamed for humanity’s downfall: humanity was never predestined to fall, but instead chose disobedience of their own accord.

Nevertheless, God acknowledges that humankind will be tricked into their downfall, and will not fall through conscious malice as Satan did; thus, God is willing to show humankind mercy as long as a suitable sacrifice is made in their place. The loving Son offers himself as a ransom for the salvation of man from eternal death, and is exalted in Heaven with sacred songs.

Meanwhile, Satan makes his way to the gates of Heaven. From there he flies to the Sun and, disguised as a lowly angel desirous to gaze on God’s works, seeks directions towards the home of Man from the angel Uriel. Uriel is fooled by Satan’s trickery, and Satan finds himself finally on the edge of Paradise.

Standing on Mount Niphates in full view of Eden, Satan is struck by regret over the sufferings he inflicted in Heaven, and doubts the sufferings he is yet to inflict upon the Earthly innocent.

The passionate soliloquy that follows provides one of the most moving moments of introspection in the entire poem: Satan reflects upon his ambition; the folly of his rebellion against his loving God, and his endless despair, for which he has no-one to blame, he realises, but himself. However, believing that repentance is impossible, too stubborn to submit himself to God, and too proud to turn back on his lofty promises to his followers, he confirms himself more deeply in evil than before. The fear and anger in his face betray his disguise to Uriel who is watching from afar.

Satan leaps over the bounds of Paradise in the shape of a cormorant, and perches upon the Tree of Life, from which he can see the entire garden of Eden, a pastoral ‘Heaven on Earth’, luscious with verdant life, nourishing streams, and ‘ambrosial fruit[s]’.

Satan gazes upon Adam and Eve for the first time, taking in their God-like forms, their untainted nakedness, and their complete freedom from guilt or shame. He also observes Eve's absolute devotion to Adam.

The sight of their peaceful innocence provokes further reflection from Satan; he dwells with pity on their coming ruin. Still, revenge compels him to do what he would otherwise hate. Satan excuses his ‘devilish deeds’ and shape-shifts into different animals to spy on the pair.

Satan overhears Adam say that the sole condition of their life in Paradise is that they must not eat from the Tree of Knowledge, lest they bring death into the world. Eve confirms this and recounts her earliest moments in Paradise, along with her first encounter with Adam. The pair embrace lovingly.

Witnessing this, Satan is filled with envy, and reflects bitterly upon his own torment. He questions why God so unreasonably denies Adam and Eve the fruits of Knowledge, and he resolves to tempt them to eat from the Tree with the promise that it will exalt them to the status of Gods.

As the sun sets, Uriel flies to Gabriel to warn him that an evil spirit has managed to gain entry to Paradise. After a long day’s work in the garden, Adam tells Eve that they should take to their bower to rest; Eve obeys. The pair praise the night and engage in loving sexual congress, entirely free from shame in their unfallen state.

The angels search the garden and find Satan, disguised as a toad, squatting next to the sleeping Eve, attempting to implant corrupting visions in her imagination. When touched with a spear, Satan returns to his original shape. At first, Satan prepares to fight Gabriel, ashamed and enraged by the Archangel’s comments on Satan’s fallen state; but with a warning from the Heavens, Satan flees.

Book 5 is a strange mixture of the domestic and the divine. It opens in the intimacy of Adam and Eve's bower at dawn: Eve is in an uneasy sleep, the words Satan has whispered into her ear troubling her with alien notions of impiety and disobedience. 

Adam wakes his wife, and she tells him her dream, in which an angel tempted her to taste the fruit of Knowledge with alluring praises of its empowering effects. Troubled, Adam recognises the signs of evil, but cannot guess at its source, and his attempt to reason Eve out of her fears is only half-successful. 

They then begin the business of the day, hymning their praises of God and his wondrous creation. Their song restores their disturbed spirits, and they set about the task of pruning the abundant bounty of the garden of Eden. 

God, watching Adam and Eve at work, instructs the angel Raphael to pay them a visit. He is to talk to them of their enemy, Satan, and warn against his lies and trickery, advising them to use their free will wisely - in case, after they've fallen, Adam and Eve should complain that ignorance of evil left them vulnerable to its allure.

Raphael, majestically winged and heavenly perfumed, arrives in Eden. Adam tells Eve to prepare a splendid meal for their honourable guest. 

Angel and man sit down to eat together, and Raphael explains free will and disobedience to Adam; he relates the cautionary story of the rebel angels' fall from Heaven.     

Raphael tells Adam how, before Earth’s creation, God summoned his host to hear a divine decree: the Son, Christ, has been begotten, and appointed Lord of all the angels, God’s vicegerent. 

The angels celebrate with festivities and feasts, but there is a disaffected angel among them: the archangel now known as Satan feels jealousy and wounded pride, and determines on insurrection. 

Satan, charming and well-respected, lures ⅓ of the angelic host under pretence of gathering the angels to worship their new ruler. Instead, he makes an eloquent speech protesting against  'prostration vile' to God and now his Son, rejecting servitude, and questioning the divine pair’s right to rule. 

His persuasive rhetoric convinces most of his hearers, but there is one angel who refuses to be swayed. Abdiel denounces Satan as a blasphemous ingrate, and asserts God's supremacy as creator. Alone untempted, he predicts the rebel angels' destruction by God, and leaves their camp.

Raphael continues with the story. He recounts how Abdiel returns to find God’s army of angels preparing for war with Satan’s rebel forces.

The angels praise the pious Abdiel for alone withstanding Satan’s influence, and lead him to God’s throne, where God commands His angelic legions to drive the insubordinates out of Heaven.

Heaven grows tempestuous, and with the loud blare of a trumpet, God’s forces and the fallen host enter into furious battle. The warrior Archangel Michael cuts Satan down with his God-given sword, and, after a host of losses, Satan's army is forced to retreat.

Night falls, and while the good angels sleep, Satan holds a council to boost morale, proclaiming the fallen host undefeated and urging more violent arms. Satan plots the invention of a new weapon: gunpowder artillery. The fallen angels, roused by his innovation, build these new weapons of mass destruction overnight.

In the morning, battle begins again. Satan, armed with his devilish invention, catches the Heavenly host by surprise; the fallen angels bombard God’s army with a thunderous hail of cannonballs, knocking them down by the thousands. Certain that they have won, Satan and his army mock the good angels’ struggle.

But the good angels do not flail for long. Surging with divine rage and implacable strength, they pluck Heaven’s mountains straight out of the ground and rain them down upon the rebel angels. Satan’s army, overwhelmed at first, respond by doing the same.

God, safely enshrined in Heaven, had foreseen all of this: in fact, he had permitted it, for it would give his almighty Son the opportunity to prove himself the worthy ruler of Heaven, God’s chosen king, by defeating Heaven’s enemies.

The Son rides out in God’s chariot, and endowed with His Father’s strength, strikes the terrified rebels with thunderous arrows, driving them out of the Walls of Heaven.

For nine days, Satan and his rebel angels fall through the black abyss of Chaos, until they are engulfed, finally, by the fiery depths of Hell. Meanwhile, the Son returns triumphant to a victory parade and is hailed by Heaven’s angels as their rightful King.

Raphael finishes his tale with a clear warning to Adam: Satan, envious of their lot and adamant on revenge, plots to seduce Adam and his ‘weaker’ half, Eve, to disobedience; but the ‘rewards’ of transgression are terrible, and God’s punishment of the fallen angels should serve as a clear lesson, that eternal misery comes to those who choose disobedience against God.

Book 7 begins with another appeal for divine inspiration, as Milton, now halfway through his poem, invokes the Muse Urania to guide him safely down from Heavenly matters to matters set on Earth.

Milton's invocation of Urania is directly paralleled with Adam's request for knowledge from Raphael; for back on Earth, Adam asks the Archangel for more divine wisdom, so that they might know how and why God created the World in the first place.

After warning Adam of the dangers of an excessive thirst for knowledge, Raphael proceeds to explain how God created the world after Satan was banished from Heaven to re-people Heaven’s lost numbers. God initiated the Creation through the Son, his Word: the Son looks out onto Chaos and with God’s ‘omnific’ voice, creates Earth and orders all its elements.

The rest of the book charts the six days of Creation much as it is described by the account in Genesis.

The last to be created is man, made in imago dei. God moulds Adam out of the dust of the ground, and creates Eve to be his mate. Offering them the bountiful Garden of Eden, he gives them only one command: to temper their appetite and shun the fruit of the Tree of Knowledge of Good and Evil, lest they should die.

At the end of the sixth day, God returns to Heaven to behold his newly created world. Book 7 ends with a heavenly celebration of this last masterpiece of creation.

Book 8 continues the conversation between Raphael and Adam. Eve, present at first, leaves the two to talk in private, preferring to hear her husband relate the angel's words to her later.

Adam asks Raphael about the celestial movements of the planets and stars, but Raphael leaves him unanswered, encouraging him to turn away from Heaven’s lofty secrets. He warns Adam to be satisfied with what God has given him, and to resist the urge to dream of hidden matters beyond his state.

Cleared of doubt by the angel's reply, Adam begins to recount his earliest memories on Earth.

He recalls how a dreamlike Presence led him to Eden and introduced himself as God the Creator: He gives Adam dominion over Paradise, but lays down one single commandment in return, a pledge of Adam’s obedience, that he not eat the fruit from the Tree of Knowledge. If Adam should break this command, he will be made mortal and expelled from Eden.

God allows Adam to name Earth’s animals, as to consolidate man’s dominion. Seeing the animals in pairs, Adam enquires after a companion for himself. God is impressed by his reasoning, and reveals that He intends to make man a perfect mate. Placing Adam in a stupor, God creates Eve from Adam’s left rib.

Upon seeing Eve’s beauty in person, Adam is overjoyed with this ‘fairest of [...] gifts’; he names her Woman, and proclaims her his beloved wife.

Upon hearing this, Eve flees from Adam; but her modest flight only makes her more desirable to him. Adam runs after her and convinces her to enjoin herself to him in the nuptial bower. Adam’s love for Eve is his greatest passion, but with her only he is worryingly ‘weak / Against the charm of beauty’s powerful glance’.

This leads to a discussion on the nature of love and sex. The day is drawing to a close, and Raphael departs, reminding Adam to resist the temptations of untempered passion and pleasure.

Book 9 opens with a personal prologue: Milton, genre-conscious as ever, discusses the hybrid genres of Paradise Lost, and justifies his arduous poetic project. With Raphael’s departure from Paradise, the poem is said to be, from here on, of the tragic-heroic mode. Book 9 will tell of the tragedy of humanity’s Fall, and it is in this book that the fatal act of disobedience will take place.

Milton intends to redefine classical heroism in Christian terms, he says; he means to demonstrate how the narrative of the Fall, its consequences and Christ’s salvation — the novel subject for his Christian epic — is superior to traditional heroic subjects for its lofty portrait of ‘patience and heroic martyrdom’.

The poem turns to Satan. Having compassed the earth for more than a week, Satan finally decides to sneak back into Paradise, plotting humanity’s destruction. Concealed by the darkness, and ‘involved in rising mist’, Satan infiltrates the garden, and proceeds to roam the Earth in search of a serpent to disguise himself with.

Satan bursts into passionate lament. Tortured by his inner inability to enjoy the delights of Earth’s beauty, and consumed with hate and jealousy, he soliloquises on his inward grief. His bestial form and fall from Godhead disgust him, but ambition and revenge have debased him beyond redemption: his only desire is to spite God and bring about humanity’s destruction. Satan finds a sleeping serpent to possess. He enters it through its mouth, and lies in wait.

As day dawns, Eve suggests that they divide their labours in the garden to work more effectively. Adam admits the sense of Eve's suggestion, and despite voicing at some length his fear that their separation might expose her to Satan’s temptation, after which the pair debate rather tensely, he eventually allows her to go. The narrator proclaims against this folly, unable to let the 'event perverse' (405) pass without lament.

Satan catches sight of Eve, and is momentarily disarmed by ‘[h]er heavenly form / Angelic’. Before long, he talks himself back into hatred. He approaches Eve in glittering serpentine form, ready to begin his ‘fraudulent temptation’.

Satan opens in flattering tones, with a high-flying encomium to Eve’s beauty and sovereignty. Eve marvels at the serpent's human voice. Satan leads her to the very tree which he alluringly claims gave him the powers of Reason and Speech. She resists when she discovers it is the forbidden Tree of Knowledge, but Satan persists, tempting her with persuasive arguments about the boundless knowledge and enfranchisement that could be hers if only she tasted the ‘intellectual fruit’.

Astonished by Satan's skilled command of language and Reason, persuaded by his flattery, and in hunger of knowledge, liberty and Godhead, Eve persuades herself to succumb:

Forth-reaching to the Fruit, she plucked, she eat.

Earth felt the wound, and Nature from her seat,

Sighing through all her works, gave signs of woe

That all was lost.

Eve feels the greedy rush of knowledge. She considers keeping its fruits to herself: with ‘the odds of knowledge in [her] power’ she may finally be able to live as Adam’s ‘equal’, ‘for, inferior, who is free?’. Nevertheless, afraid to lose Adam, jealous that he may take another wife if the fruit does prove to be fatal, she decides to bring her spouse a sample.

Adam is horrified by Eve’s transgression, but he cannot bear to be separated from her, even if it means facing death. He resolves to follow the only path his love allows: he completes the ‘mortal sin / Original’ by eating the fruit.

Intoxicated, the pair are filled with carnal lust. After making love, they wake to find themselves miserably naked. Scrambling to cover themselves with fig leaves, they are filled, for the first time, with immeasurable shame, and weep in the face of their lost innocence. With Adam and Eve now enslaved to their passions, the turbulent powers of ‘anger, hate, / Mistrust, suspicion, discord’ take over. Book 9 ends with the pair arguing bitterly.

Paradise’s Guardian Angels are miserable upon hearing the news of Satan’s infiltration, and return to Heaven to explain what has befallen. God reassures them that Adam and Eve fell of their own accord. Reiterating his ‘mortal sentence’ for their transgression, God sends his merciful Son to judge Adam and Eve accordingly.

At sunset, the Son arrives on Earth to issue his judgments upon the pair: for Eve and womankind, pain in childbirth and a future of submission; for Adam and his descendants, a life of hard toil; and for both (ultimately) death. Pitying their shame, the Son clothes Adam and Eve in animal hides, and re-ascends to Heaven.

Meanwhile, strengthened by Satan's victory, Sin and Death build an infernal bridge across Chaos to ease their passage into Earth.

Satan returns victorious to the bridge, where he is greeted with adorations from his daughter. Urging Sin and Death to establish their dominion upon the mortal world, Satan continues his journey back to Hell.

In Pandemonium, Satan addresses his followers victoriously, but is greeted with ‘a dismal universal hiss’: Satan and the fallen angels are transformed by God into serpents, an apt punishment for their sins. As a false grove of Forbidden Trees springs up before them, the devils are cursed with never-ending hunger. Fruits turn to ashes before their temptations can be quenched.

With Sin and Death wreaking havoc upon Earth, God foretells the Son’s eventual victory and humanity’s redemption. In the meantime, God tasks his angels to make alterations to the postlapsarian world, introducing changing seasons and violent storms to match humanity’s fallen state.

Consumed by guilt, Adam laments his despair and the suffering he has borne upon humanity. Bemoaning the female sex, he bitterly spurns Eve’s attempts to console him. Eventually, the pair begin to reconcile, and Adam conceives of hope. Together, Adam and Eve supplicate and repent.

The Son presents Adam and Eve’s prayers to God, and petitions for their sufferings to be eased through His sacrifice. God accepts the Son’s requests, but decrees that Adam and Eve can no longer dwell in Paradise. God sends Michael to evict the fallen pair from Eden, but permits the Archangel to temper their discontent by enlightening Adam of future days, including the incarnation of Jesus Christ on Earth.

Meanwhile, Adam and Eve muse on the peace brought on by prayer, though their satisfaction is soon disrupted by ill omens auguring Michael’s arrival. Michael explains to Adam that God has postponed their deaths to give them a chance at repentance, though he no longer permits them to dwell in Paradise. The news of their exile prompts their grief, but Michael reminds them that God’s love is omnipresent, not confined to Eden alone.

Sending Eve to sleep, Michael bestows upon Adam visions of the sufferings and sins of his descendants, sins derived from Adam’s original, starting with the first death – Abel’s murder at the hands of his own brother – and concluding with the events of the Flood. Michael highlights the virtuous exceptions of Enoch and Noah, who were rewarded with eternal life in Heaven.

Adam’s mortal sight grows weary. Michael decides to narrate the rest of what is to come, cautioning hubris in the tale of Nimrod and Babel, and highlighting the faith of Abraham, who is promised land by God to start a new community of chosen people, and whose work and strife is continued by his progeny, Isaac, Jacob and Moses.

Michael finally arrives at the coming of the Messiah. He reassures Adam that the Son of God, born of a virgin mother, will overcome Satan’s works and save humankind from their sentence of suffering and eternal death through his incarnation, crucifixion, resurrection, and second coming. Christianity will spread through Christ’s Word, and the deserving will be rewarded in Heaven. Adam rejoices that the Son of God will be born of a human descendant of his, and marvels at the good that will eventually come of his original sin.

Michael reminds Adam that Satan’s influence will continue after the spread of Christianity: priests will build churches ‘to their own vile advantages’, tainting God’s truth with ‘superstitions and traditions’. Nevertheless, Christ’s second coming will defeat Satan’s perversion and purify the Earth once and for all.

Comforted about the conquest of good over evil, and strengthened by the knowledge that good deeds and faith in God will be a Paradise of their own, Adam awakens Eve from her gentle slumber, and the two are gently led out of Paradise by Michael:

They looking back, all the eastern side beheld
Of Paradise, so late their happy seat,
Waved over by that flaming brand, the gate
With dreadful faces thronged and fiery arms:
Some natural tears they dropped, but wiped them soon;
The world was all before them, where to choose
Their place of rest, and providence their guide:
They hand in hand with wandering steps and slow,
Through Eden took their solitary way. (12.641-9)