This epic poem tells the reader the story from Dante’s alter-ego, the Piligrim, point of view. The Piligrim starts his travel to the Heaven through Hell and Purgatory. He gets lost in the wild forest and attacked by the beasts - a lion, a leopard and a she-wolf - but the spirit of the ancient Roman poet, Virgil, meets him and shows him the way. Virgil says he was sent by the three heavenly ladies (the Virgin Mary, Saint Lucy, and Beatrice) to help the Piligrim reach salvation.
Virgil guides the Piligrim to the Underworld, telling him about each layer of Hell or Inferno - an enormous, funnel-shaped cave that goes deep, to the center of Earth. Every layer metaphorically depicts the punishment for different sins and conditions become harsher and harscher as Virgil and Piligrim proceed downwards.
The entrance to Hell is marked with the sign “Give up hope you, who enter”. Behind it lies a bleak place where souls wait for Charon to transfer them further. Some souls that have never chosen neither good nor evil are staying there. Charon is furious to see a living person in his domain, but Virgil says that they came here by Lord’s command. Charon lets them board his boat and transfers them to the circle of Limbo where the souls of pagans rest. They aren’t guilty, but, as oblivious to God, they can’t enter Heaven and shall stay in Hell in eternal idleness and sorrow. The Piligrim briefly talks to the greatest minds of that age before going deeper.
The second circle of Hell is guarded by the demon Minos who decides where each sinner should go. Minos is pacified by Virgil and lets them enter the realm of the Lustful. The Piligrim sees the souls of notorious lovers, a hurricane plays with them throwing them around and not allowing to touch each other again. The Piligrim talks to the soul of Francesca de Rimini who tells him her tragic story about being involved in an adulterous affair with her brother-in-law. Their passion led to their death and now they shall suffer here for eternity. In deep sorrow, the Piligrim passes out to regain consciousness near the entrance to the next layer of Hell.
This circle hosts the souls of gluttonous people. They spent their afterlife in mud and mire guarded by Cerberus - the terrifying three-headed dog ready to tear everyone apart. The Piligrim talks to Ciacco, a former Florentinian who enjoyed making and telling gossips. Ciacco asks the Piligrim to remind living people about him.
The fourth circle of Hell belongs to the avaricious and the prodigals. There are no persons that Piligrim can talk to and the words of the circle keeper don’t make any sense. There are surprisingly lots of clergy and also there are spenders, gamblers and cheapskates. The inhabitants of this circle have their heads attached backwards, so they bump into each other. Every day they roll enormous rocks to the center of the circle and then collide, argue and return the same way to their places not knowing where they go.
On the fifth circle stay the wrathful and the sullen. The sullen souls are completely submerged in the waters of the swampy river Styx, while the wrathful ones emerge from it trying to fight their way out. There the Piligrim meets Filippo Argenti. Behind the river stays the city of Dis. The circle guardian, Phlegyas, helps them make their way across the Styx. Furies guard the city gates but Virgil commands them to let them go and they allow the Piligrim and his companion to enter Dis - the city in the sixth circle of Hell. From this city the Lower Hell starts, where the souls are punished for sins of violence and fraud. The Piligrim sees the cemetery in the city where fire emerges from the graves - there are heretics inside. They are suffering much more than everyone he saw before. In Upper Hell the souls are guilty of giving up to their desires without doing any harm by their own will. But in Lower Hell souls are tormented for conscious evil, so their guilt is much more severe.
The seventh circle, guarded by Minotaur, holds the violent souls. It consists of three parts. In the first part there is a boiling river of blood - Phlegethon. The souls who were violent to other people boil there. Second part is covered by the living and weeping trees and bushes which display human emotions - those who committed suicide (were violent towards themselves) turned into them. The third part, where the burning snow falls tormenting the souls inside, is for those who committed violence towards God or Nature’s laws.
Next circle is a circle of Fraud. It is called Malebolge, because it consists of 10 bolges (ditches). Each of them is for different kind of sin: panders and seducers; flatterers; simonists; diviners, astrologers and magicians; barrators; hypocrites; thieves; fraudulent counselors; sowers of discord and schism; falsifiers of metals, persons, coins and words. In every Bolge the Piligrim talks to the soul and hears their story.
The last, ninth circle of Hell is in the centre of the Earth. The souls here are frozen in the icy lake Cocytus. The traitors are tormented there: traitors to kin, traitors to homeland, traitors to guests and traitors to benefactors. In the center of Cocytus sits Lucifer and his clapping wings keep the lake frozen. Lucifer has three faces, the mouth of each is chewing one traitor: Judas, Brutus and Cassius.
Sneaking past Satan Virgil and the Piligrim enter the tunnel that leads them to the other side of the Earth. They enter the Purgatory, a mountain on the opposite side of the world that was formed because of Hell creation. The mountain has seven terraces based on seven deadly sins that are also divided to pre-Purgatory, Purgatory and earthly Heaven, similar to Upper and Lower Hell. If in Hell the souls are condemned forever, here they still suffer, but they have hope to reach salvation - and Heaven.
Before entering the Purgatory an angel appeared near the sleeping Piligrim and wrote seven letters for seven deadly sins on his forehead. While he and Virgil go through every terrace, letters, one after another, are washed away from his skin. The Piligrim asks Virgil about his deceased love, Beatrice, who he hopes to see in the afterlife. They go up until they reach the top of the mountain surrounded by the circle of fire. The Piligrim is afraid to go through flames but Virgil tells him not to be afraid and he falls asleep again.
When the Piligrim wakes up, the spirit of Beatrice awaits him in the Earthly Heaven where Adam and Eve were exiled from. Now Beatrice is his guide to Heaven.
Heaven consists of ten spheres with Earth in the middle. Each sphere or sky is dedicated to one virtue. The first sphere of Moon is the home to nuns who were abducted from monasteries and married away. Though their celibate vow was broken, they can’t reach the higher skies.
The second sky of Mercury is dedicated to virtue of fortitude. The Piligrim meets the emperor Justinian there. Justinian understands that this sky is his limit, because he did good deeds because of himself and his glory.
The souls full of divine love inhabit the third sky of Venus. Carl Martell speaks to the Piligrim saying that a man can be successful and happy when he does what he loves to do and no one born warrior will make a good priest.
The fourth sky of Sun is a domain of wisdom. There the Piligrim talks to lots of souls of ancient people, discussing theology questions and thinking of future resurrection.
The fifth sky of Mars serves as home to warriors who died in the name of faith. They are resting there listening to the divine hymns, but some of them are upset that their glorious times are gone.
The sixth sky of Jupiter is of just rulers. The lights of souls here form the images of eagle and that eagle, the embodiment of justice, speaks to the Piligrim. But it becomes known that there are individual souls of king David, Hezekiah, Trojan and other rulers of ancient times.
Seventh sky of Saturn is embodiment of temperance. The Piligrim meets the soul of Peter Damian there and discusses sad state of the church with him.
Eighth sky is the sphere of fixed stars, of Faith, Hope and Love. There are souls of church triumphants singing glory to Virgin Mary. The Piligrim looks down from this sky and sees the Earth and all the places he visited before.
Ninth sky is the Primum Mobile (First Moving Sphere). It is the last sphere of physical Universe. It is moved directly by God and its movement causes all the other spheres to move also. The angels live here. The Piligrim sees God surrounded by nine circles of angels. Here Beatrice explains him everything he saw before and bitterly criticizes the state of modern church.
They go to the tenth sky, the Empyrean that lies beyond the physical Universe. Here Beatrice becomes even more beautiful than before and envelops the Piligrim in light preparing him to see God. The Piligrim sees an enormous rose, each petal of which is an enthroned soul. Beatrice also has her place in that rose. She returns there, saying that the Piligrim went beyond theology and St. Bernard will be his next guide.
St Bernard talks to the Piligrim about predestination and prays to Virgin Mary for him. Finally the Piligrim comes to God appearing as three equal circles occupying the same space, representing the Holy Trinity. The Piligrim can’t comprehend what he sees but his soul becomes finally aligned with God’s love.