Although still mourning the loss of his companion, the palmer, Sir Guyon decides to continue his quest for the Bower of Bliss. While passing through a dense thicket, his attention is attracted by a clank of metal, and peering through the branches he descries an old, dirt-encrusted man, surrounded by mounds of precious stones and coins, which keep dropping through his fingers. This creature is Mammon,—God of Wealth,—who is so busy counting his treasures that at first he pays no heed to Sir Guyon. When questioned, however, he boasts he is more powerful than any potentate in the world, and tries to entice Sir Guyon to enter into his service by promising him much gold. For a moment Sir Guyon wavers, but finally decides not to accept the offer until he has ascertained whether Mammon's riches have been honestly gained. To show whence he draws them, the money-god now conveys Sir Guyon to the bowels of the earth, and there lets him view his minions mining gold, silver, and precious stones, and thus constantly increasing his hoard. But, although sorely tempted, Sir Guyon perceives that Mammon's workmen are oppressed by Care and driven by Force and Fraud, who keep them constantly at work and never allow Sleep to approach them. This discovery makes him decide to have nothing to do with Mammon's treasures, although he is led into a hall where hosts of people are paying homage to the money king's daughter, who, he is told, will be his bride if he will only accept her father's offers. Coldly rejoining that his troth is already plighted, Sir Guyon refuses, only to emerge from this hall into a garden, through whose branches he catches fleeting glimpses of the underworld. In one of its rivers he even beholds Tantalus, undergoing torments from hunger and thirst, in punishment for sins committed while on earth.
After being subjected for three days to all the temptations of the underworld, Sir Guyon is led back to the light of day, where Mammon—who bitterly terms him a fool—abandons him.
The story now returns to the palmer, who, after watching Sir Guyon out of sight, wanders along the stream in quest of a vessel to follow his master. Several days later he manages to cross, only to hear a silvery voice calling for aid. Bursting through the thicket, he discovers Sir Guyon, lying on the ground, watched over by a spirit of such transcendent beauty that the palmer realizes it must be an angel even before he notes its diaphanous wings. This ministering spirit assures the palmer that Sir Guyon will soon recover, adding that although unseen he will continue to watch over him, and will help him to escape from all the dangers along his path. Then the heavenly spirit vanishes, and, while the palmer is bending over the fainting Sir Guyon, he sees two knights draw near, preceded by a page and followed by an old man. These knights are Deceit and his brother, who have been brought hither by the old man Archimago, to slay Sir Guyon whom they hate.
Drawing near, these ruffians thrust the palmer aside, but, while they are stripping the unconscious man of his armor, another knight suddenly draws near and attacks them. One giant, being without a sword, seizes that of Sir Guyon, although Archimago warns him that as it once belonged to his antagonist, it will never harm him.
Prince Arthur, for it is he, now overcomes the ruffians, to whom he generously offers life, provided they will obey him hereafter. But, when they refuse these terms, he ruthlessly slays them, and their spirits flee shrieking "to the land of eternal night."
At this moment Sir Guyon recovers his senses, and is overjoyed to find the palmer beside him and to learn that Prince Arthur, who rescued him from the ruffians, is not far away.
After a brief rest, Prince Arthur and Sir Guyon depart together, the former explaining how anxious he is to do anything in his power for Queen Gloriana, whom he devotedly loves although he has never yet seen her. Conversing together, the two ride on to a castle, where no heed is paid to their request for a night's lodging. They are marvelling at such a discourtesy, when a head is thrust over the battlement and a hoarse voice bids them flee, explaining that the castle has been besieged for seven years past by barbarians lurking in the forest, against whom no knight has ever been able to prevail.
It is while the watchman is thus accounting for his inhospitality, that a rout of hungry barbarians bursts out of the forest and attacks Sir Guyon and Prince Arthur, both of whom fight to such good purpose that they utterly annihilate their assailants. Happy to be delivered from these foes, the inhabitants of the castle then open wide their gates. Our knights spend several days there resting from their labors, and perusing sundry books where they learn the history of all the British kings. Meantime the palmer, who has followed them thither, forges chains and a steel net, with which to capture and hold the witch Acrasia when the right time comes. When he has finished manufacturing these objects, he persuades Sir Guyon to start out once more. Reaching the water again, they board a vessel, which bears them safely past the Magnetic Rock, over the Sea of Gluttony, etc., to an island, whose beauty human imagination cannot conceive.
On landing, the travellers are surprised to encounter strange monsters, and to be enveloped in dense mists, through which they hear the flapping of bat-like wings and catch glimpses of harpy-like creatures. Knowing monsters and mists are mere delusions, Sir Guyon pays little heed to them, and the palmer soon disperses them by a touch from his magic staff. Still bearing the steel net and iron chains, this faithful henchman follows Sir Guyon into the enchanted bower of Acrasia, where he explains to his master that the animals he sees owe their present forms to the enchantress' power, for she always transforms her visitors into beasts!
Through an ivory gate,—on which is carved the story of "The Golden Fleece,"—the adventurers enter a hall, where a porter offers them wine. But Sir Guyon, knowing a drop of it would have a baleful effect upon the drinker, boldly dashes it out of his hand. Then, threading his way through the Bower of Bliss, he reaches its innermost grove, although Phaedria tries to detain him by offering him sundry pleasures. Pressing onward, Sir Guyon finally catches a glimpse of Acrasia herself, reposing upon a bed of flowers, and holding on her lap the head of an innocent youth, who is helpless owing to her spell. Silently signalling to the palmer, Sir Guyon spreads out the steel net, which they fling so deftly over witch and victim that neither can escape. Then Sir Guyon binds Acrasia fast, threatening to kill her unless she removes the spell which she has laid upon her captives. All the beasts on the island are therefore soon restored to their natural forms, and all profess gratitude, save one, whom the palmer grimly bids continue to be a pig, since such is his choice! Having thus happily achieved this quest, Sir Guyon and the palmer leave the island with Acrasia, who is sent under strong guard to the court of the Fairy Queen, where Gloriana is to dispose of her according to her good pleasure.