The noble Duke Theseus of Athens is on his way home from his invasion of Scythia, where he has won a wife, Hippolyta, and a sister-in-law, Emily. Sounds like a pretty successful trip, right? Along the way, Theseus & Co. meet a group of crying women. They beg Theseus to take vengeance on Creon, King of Thebes, because of his refusal to allow them to give their husbands' bodies a proper burial. Theseus agrees and beats Creon. In the process, he wins two noble Theban hostages, cousins Palamon and Arcite.
Theseus throws Palamon and Arcite in the slammer (a tower next to his garden), without ransom. One day in early May, Emily walks in the garden, gathering flowers. Palamon sees her from the prison window and immediately starts crushing on her. He's so smitten that he cries out. Hearing his cry, Arcite runs to his cousin. But as soon as he lays eyes on Emily, he falls for her too. The knights argue about who gets dibs on Emily. Arcite finally decides that it's a dumb argument to have; since both knights will be in prison forever, they'll just have to love Emily from afar with no hope of consummation.
Or maybe not. Soon, Arcite gets out of jail because he and Theseus have a mutual friend, who petitioned to get Arcite released. The only catch is that Arcite has to leave Athens and never set foot in the city again. Arcite moans and groans and feels sorry for himself, convinced that Palamon is better off than him because he gets to see Emily every day. Palamon, on the other hand, thinks that Arcite is a lucky dog because he can assemble an army to win Emily in battle.
Arcite returns to Thebes for a while, but, unable to stay away from Emily, quickly returns to Athens disguised as a servant. He works his way into Theseus's household, becoming Emily's manservant.
Meanwhile, Palamon has managed to escape from prison. He takes shelter in a grove of trees not far from the palace, planning to continue his journey under cover of nightfall. And – surprise, surprise – Arcite happens to go walking in that same grove. Palamon doesn't recognize him at first because of his disguise. When Arcite begins to speak of his love for Emily (because, you know, emo lovers always talk to themselves about their crushes), though, Palamon figures out who he is and leaps from the bushes, outraged. He and Arcite bicker. Arcite challenges Palamon to a duel, promising to return the next day with armor and weapons for Palamon, to ensure a fair fight.
The next day comes, and the two knights begin their duel. Duke Theseus and his party, out hawking, happen to come across the two knights as they battle. Theseus orders them to stop. When he finds out who they are at what they're fighting about, he at first wants to put them to death. But when the ladies, especially Hippolyta and Emily, beg for mercy, Theseus reconsiders. The Duke admits that he, too, has done some pretty stupid things for love.
Theseus decides that each of the knights must return in one year's time with one hundred knights, in order to fight an epic joust. The winner will get Emily. The knights agree, and ride home to Athens to gather knights. Meanwhile, Theseus pours time and money into building a huge stadium for the joust. It's like he's prepping for the World Cup. The stadium is complete with temples dedicated to Venus (goddess of love), Mars (god of war), and Diana (goddess of the hunt).
After a year has passed, Palamon and Arcite return to Athens, where everybody is ready to watch the competition and party. On the morning of the joust, the two knights and Emily visit the different temples. Palamon prays to Venus to grant him Emily, while Arcite asks Mars for victory in the joust. Emily, on the other hand, asks Diana to grant her perpetual virginity. (Guess she doesn't want to marry either of these guys.) Only Emily's request is refused. The knights' requests cause a conflict between Mars and Venus in the Heavens, but Jupiter (the king of the Gods) figures out a way to please both of them.
The joust begins, and many captives are taken. The fighting is fierce on both sides. In the end, Palamon is captured, and Arcite wins. On his victory ride, an earthquake in the stadium causes Arcite's horse to trip, sending him headfirst to the ground. Despite cracking his head pretty hard, everyone is sure that Arcite will recover. That night the people of Athens celebrate the upcoming marriage of Emily and Arcite.
But Arcite doesn't recover. He dies with Emily and Palamon at his bedside, using his last breath to tell Emily what a great guy Palamon is. Theseus arranges a fancy funeral for Arcite, after which Palamon returns to Thebes in mourning. He doesn't stay in Thebes very long, though. Theseus's counselors want an alliance between Athens and Thebes, and think that a marriage between Palamon and Emily would be just the thing. Theseus gives a long speech about how death is a part of God's plan for the world. At the end, he recommends that Palamon and Emily marry. They agree, and the story ends with a big, happy wedding.