After the deaths of Achilles and Ajax, the Greeks are still no closer ending the war with Troy.
Odysseus decides to capture the Trojan seer Helenus, who has left Troy for Mt. Ida. Angry at Priam and the Trojans, Helenus apparently offered no resistance. When the Greeks asked him when Troy would fall, Helenus gave them a series of conditions, which must be satisfied before the Greeks could have their victory. The conditions were that Neoptolemus and Philoctetes must be persuaded to fight for the Greeks, and the Palladium must be stolen from within Troy's walls.
Odysseus then set about satisfying these conditions. Disguised as a beggar, he enters Troy to steal the Palladium, which was an image of Athena given to Dardanus by Zeus. Inside the city, he is discovered by Helen, but she aids him in his task. With her help, he steals the Palladium and returns to the Greek camp.
Then he sets out with Phoenix to fetch Neoptolemus. They first sail to Lycomedes' court, where Neoptolemus is living. The young man needs little persuasion, and is eager for the glory of war. Odysseus gives to him the armor of Achilles, which had earlier led to the death of Ajax.
Then, the three sail to Lemnos, where Philoctetes has been living for ten years, surviving only by hunting with his bow. Knowing that Philoctetes would rather kill him than leave the island, Odysseus decides to trick him. He has Neoptolemus, whom Philoctetes does not know, approach him. Neoptolemus claims that he will take Philoctetes back to Greece, and he even persuades the poor man to lend him his bow of Heracles. Philoctetes agrees.
Once on the boat, however, Neoptolemus has second thoughts about his actions. He decides to take Philoctetes back to Greece, fulfilling his earlier promise. Odysseus is upset, but the clever-talker cannot convince him otherwise. As they sail, however, Heracles, now a god, appears and commands Philoctetes to fight at Troy.
When they arrive in Asia, Neoptolemus proves to be good soldier, just like his father. The great archer Philoctetes kills Paris with his bow. Troy, however, still does not fall. Most of the Trojan leaders are dead, and the Trojans no longer leave the city to fight the Greeks. Troy's massive walls, however, prove to be impenetrable.
At last, the clever Odysseus devises a plan to end the war. They construct a massive, hollow horse, under the direction of the artisan Epeius. Chosen Greek warriors, led by Odysseus, conceal themselves in the horse. All the other Greeks board their ships and sail away. They do not sail far, however, but only to the far side of a nearby island.
The remaining Trojans observe the Greeks sailing away. Confused, they head down to the Greek camp to investigate. On the shore, they see the huge horse, as well as Sinon. Sinon, a Greek spy, says that he was left behind by the Greeks. He pleads to them for mercy, and they do not kill him.
The Trojans are divided. Some, led by Laocoon, a priest of Poseidon, do not trust the horse. He says that there are either men in the horse, or that it is a huge siege engine. He then utters the famous phrase, 'I fear the Greeks, even when bearing gifts.' At the end of the speech, for dramatic purposes he hurls a spear into the side of the horse.
Sinon then speaks up, and he explains to them that the horse has been left behind, as a gift to Athena. This is their atonement for stealing the Palladium from Troy.
After the words of Sinon, Laocoon is preparing a sacrifice to Poseidon. Suddenly, two snakes attack and devour him and his sons. This is because Laocoon has married against Poseidon's will. The Trojans, however, do not know this. They assume this to be a sign from the gods, and bring the horse within their walls. They even damage the walls of their own citadel to drag it inside.
That night, the Trojans throw a huge party. After most have passed out from the revelry, Sinon stealthily goes to the wooden horse, and releases the Greek soldiers inside. They then make their way to the city walls, and open the gates. Outside, the entire Greek army is waiting. They had sailed back to Troy earlier that night.
With the Greek army inside the walls, the remaining Trojans are quickly defeated. Even their citadel was not safe, for the walls were damaged while bringing the wooden horse inside. As he clung to the altar of Zeus, Priam was killed by Neoptolemus. Cassandra is raped by Ajax of Locris in the temple of Athena. Astyanax, the young son of the dead Hector, is thrown from the walls at the urging of Odysseus. The riches and women of Troy are divided among the Greek captains. Of the Trojan princes, only Aeneas escapes alive.