Midway through his life, Dante Alighieri is waylaid by a dead Roman poet, Publius Vergilius Maro (a.k.a. Virgil). Virgil offers to take Dante on a tour of the afterlife. It's the sort of offer you can't refuse.
Virgil (left) and Dante (right) enter Hell (center, back). It's not exactly a friendly place. Virgil reveals that he is condemned to stay forever in the part of Hell called Limbo, with the other virtuous pagans--people who lived before Jesus was born, and therefore are not Christians even if they are good, and therefore can't go to Heaven and must stay in Hell. (Except, of course, when they are playing tour guide.)
They travel down through the nine levels of Hell, encountering various gruesome punishments, a whole lot of Dante's political enemies, and an extraordinary number of popes. At the bottom, they discover that Hell is, in fact, frozen over. Here on the frozen plains of Hell, they see one of the most memorable of the gruesome punishments: a guy eating another guy's brains, pictured here in a completely serious and not at all silly way.
After this delightful excursion, Dante and Virgil continue on to Purgatory. They climb right through the earth to the other side, and then continue climbing because Purgatory is a very high mountain. Purgatory is rather like Hell when it comes to gruesome punishments, but the people here will eventually make it to Heaven, so they're all hopeful while they're being punished. Oh, and they run into another dead Roman poet who apparently secretly converted to Christianity in his lifetime, and so can tell Virgil, "Hah-hah, I'm going to Heaven and you're not." Then he does so, and Virgil is sad. Poor Virgil.
Anyway, our two intrepid explorers reach the top of Mount Purgatory, which is the Garden of Eden. They are treated to an astonishing and bizarre parade which I cannot possibly do justice to in words or pictures, and then--down comes Beatrice! Dante's old girlfriend, or at least the woman he was in love with! She'll be conducting the rest of this tour, and she's not about to put up with any nonsense.
(You can tell Purgatory and Hell are on opposite sides of the Earth because of the upside-down flames.)
Beatrice leads Dante up through the heavenly spheres. It all gets very mystical and philosophical, and there's a lot of bright white light. Finally they reach the most heavenly part of Heaven, where--[Censored! You are not holy enough to comprehend Heaven. Go back to Purgatory and try again.]
Dante receives the beatific vision and then is sent back to Earth, where he writes down his entire epic adventure.
Beatrice returns to her place in Heaven.
Virgil goes back to Limbo. He's sad because Dante will get to go to Heaven one day and he won't, or something. Awww.
Don't cry, Virgil. I'm sure there will be some other medieval poet who thinks that Greek and Roman philosophers are more interesting than choirs of angels.
Geoffrey Chaucer: Hmm, go through Purgatory and then spend an eternity with the do-gooders up top, or sneak down to Limbo and hang out with people who know how to have fun? There's a tough decision.
The end, probably.
I may or may not be sketching scenes from Geoff Chaucer's Unsanctioned Trip to Limbo.