"The Knight's Tale" tells the story of two cousins who are condemned by the great conqueror and ruler of Athens, Theseus, to live out their lives in a tower. Theseus conquers the city of Thebes, and shortly thereafter finds the injured cousins, Palamon and Arcite, his enemies. Theseus takes care of their wounds before sending them to the tower, where they live for many years. While there, they see Emelye, a beautiful woman, who also happens to be Theseus' sister-in-law, and they both fall in love with her. Palamon and Arcite argue but eventually realize neither will ever have her. Time goes on as before until a mutual friend of Theseus and Arcite asks Theseus for Arcite's freedom, and Theseus agrees but only on the condition that Arcite never returns to Athens. Arcite is able to go home to Thebes but finds himself filled with jealousy for Palamon, who still is able to see Emelye every day. Palamon, on the other hand, is afraid Arcite will come back and seize Athens, taking Emelye by force. At the end of Part I, the knight asks the readers, "Who is worse off--Palamon or Arcite?"
To summarize: Theseus, ruler of Athens, captures two of his enemies, the cousins Arcite and Palamon. From their tower prison both fall in love with the beautiful Emelye but realize neither can have her, until one day, a mutual friend of Theseus and Arcite's petitions for Arcite's release. Since Arcite can never go back to Athens, he becomes jealous of his cousin, who will be able to see Emelye every day; cousin Palamon becomes worried that Arcite will lay siege to Athens and forcibly take Emelye.