The evil magician Archimago, his plans to ruin Redcrosse and take Una for himself now foiled, manages to escape from the dungeon in which he was thrown and goes to look for new ways to cause mischief.
As he's plotting and scheming away, he comes across a knight, handsome and honest-looking, but also formidable and traveling with an old pilgrim (someone traveling for religious reasons), here called a Palmer.
Archimago thinks these two look just perfect for his evil plans and so he quickly concocts a story to feed to the unsuspecting knight.
He pretends to know of a woman who has just been raped and the knight, horrified, immediately agrees to avenge this wrong.
Archimago takes the knight to a woman who is crying and wearing torn clothing and she is so upset at first she won't say anything.
Finally, however, after Archimago prods her, she describes her rapist as a knight riding a grey horse and wearing a silver shield with a bloody cross on it (this guy should be sounding very familiar...).
The knight is surprised, because he's heard a lot of good things about Redcrosse, who he says he actually saw knighted.
But, if Redcrosse has done the things the lady says he has, this knight will bring him to justice.
The lady is very happy, but not for the reasons she's just given.
She is, in fact, the evil witch Duessa, whom Archimago has found hiding in the wilderness after Arthur defeated Orgoglio.
Because he lives to ruin knights and make them behave badly, Archimago restored Duessa to her former position so that together they could wreak havoc.
So, Archimago takes the duped knight to where Redcrosse is resting and the knight is about to charge him and attack, and Redcrosse is too, when suddenly, upon seeing the cross on Redcrosse's shield, the knight reconsiders.
Instead, he begs Redcrosse to forgive him for almost attacking him and Redcrosse, recognizing the voice of Sir Guyon (named for the first time), also apologizes, acknowledging the holiness of the image of the Faerie Queene painted on Guyon's shield.
So the two old friends put down their weapons and greet each other properly.
Then, understandably, Redcrosse asks why Sir Guyon tried to attack him and Guyon explains that he was misled into thinking Redcrosse had violated a lady.
As they're talking, the Palmer comes over and recognizes Redcrosse and blesses him and his future deeds.
Redcrosse, in reply, praises God and wishes Guyon good luck on his journeys and the two then pledge good will toward one another and Guyon goes off with the Palmer.
Guyon and the Palmer travel for a long time and Guyon performs many feats of bravery that make him famous all over the world.
One day, when the two are resting by a forest, they hear a voice crying.
The voice belongs to a woman with a baby, who says she has nothing left to live for and who is worried about her baby, but thinks the child would be better off without such poor parents.
Guyon then hears a terrible scream and finds the woman covered with blood, with a knife in her body, with a baby in her lap, also covered in blood. Next to both of them lies a knight, dead.
Guyon is at first frozen with horror at the scene, but then quickly takes the knife out of the woman and, feeling that she still has a pulse, tends to her wounds.
He then asks her what has happened to her and she, slowly regaining consciousness, is at first unable to speak, but continues to faint.
Finally, she asks Redcrosse to just let her die, and Redcrosse responds that he just wants to know what happened to her.
So, she tells her story: the knight dead beside them is Sir Mordant, her husband, who left her, Amavia, when she was pregnant to go search for adventures.
He happened to come across the evil enchantress Acrasia, who lives on a magic island called the Bower of Bliss where she tempts men into living luxuriously and immorally.
Mordant was tempted and captured by Acrasia and so Amavia decides to search for him herself, disguised as a pilgrim.
While she's searching for him, she gives birth to their child, who she then takes with her.
When she finally finds him, he's so far gone he doesn't even recognize her, but after she weans him off of the dangerous potions and drugs he's been given, the two escape.
But not before Acrasia casts a curse on him. Sure enough, he falls dead during their escape.
As soon as the lady relates this part of the story, she becomes overwhelmed by grief and dies.
Guyon is extremely sad to see this and feels defeated by the idea that death comes to everyone.
But the Palmer urges Guyon to be moderate with his emotions and to leave it up to God to bury her.
Guyon disagrees, however, and the two bury Amavia and Mordant and Guyon swears an oath of vengeance on their graves to find and punish Acrasia.