After a long and swift ride Gandalf and Pippin arrive to the great city of Minas Tirith in the early hours of the morning and have an audience with Denethor, the Lord and Steward of Gondor, the father of Boromir and Faramir. Denethor is a man of great power and lineage, who can guess much that is hidden behind one's words. Pippin tells about their journey, and about Boromir, and swears an oath of fealty to Gondor. After the audience Gandalf goes about his business, and Pippin goes out to explore the City. He meets Beregond, a soldier of the city guard, who has been sent to keep him company for a while. They talk about Gondor and its customs, and about Pippin's journey and the distant lands he had seen, and the war that is drawing near and in which Gondor seems to have no hope. Later, when Beregond has to attend to his duties, Pippin looks up his son, Bergil, and together they go to the city gates to watch the armies of Gondor coming to strengthen the defence of the City. In the evening Pippin returns to his lodgings, and in the night Gandalf returns as well, seeming worried and concerned.
Soon after Gandalf's departure the company of king Théoden is joined by a group of Rangers of the North, Aragorn's kin, accompanied by Elladan and Elrohir, the sons of Elrond. They ride together to Helm's Deep, where Aragorn looks into the palantír and wrenches it from the control of Sauron's mind. He decides to go as quickly as possible to Gondor, taking the dreaded Paths of the Dead, accompanied by Legolas, Gimli, the sons of Elrond and the Dúnedain. It will take Théoden (with whom Merry remains as an esquire) several days to muster the host of Rohan; meanwhile Aragorn and his company ride towards Edoras and Dunharrow in a straight course. There Éowyn wants to join them, but Aragorn does not permit her, saying that only Théoden could release her from her duty. The next morning the company pass through the Paths of the Dead: a kind of tunnel leading to the other side of the mountains south of Rohan. The 'Dead' are the shadows of a people of old who broke their oath to Isildur, and Isildur cursed them not to find peace until the oath be fulfilled. Now Aragorn, being Isildur's heir, summons them to help him in the war, thus fulfilling their oath. The company, followed by a great host of the shadows of the Dead, head eastwards towards Pelargir.
Meanwhile Théoden and his host ride to Dunharrow, where the army of Rohan is gathering. Éowyn awaits them there and tells them that Aragorn has gone to the Paths of the Dead; little is known of them to the Rohirrim, only a few frightening legends, and they are sure that Aragorn will never be seen again. An errand-rider of Gondor comes, bringing word from Denethor about the peril of Minas Tirith, and asking the Rohirrim (who have been allies of Gondor for centuries) for help in the war. Théoden prepares to set out on the following day, intending now to go openly across the plain, for the great cloud from Mordor has covered the entire sky with darkness. He decides that Merry should remain behind in Edoras, where Éowyn will lead the people until the king's return. Yet a young rider called Dernhelm secretly offers Merry to bear him on his horse to Gondor, and Merry gladly accepts the offer.
The following morning, when the Darkness has already covered the sky, Gandalf takes Pippin to Denethor, and Pippin receives a uniform of the Tower. Later he meets Beregond and talks to him for a while on the city walls. That very evening Faramir returns into Minas Tirith, barely escaping the winged Nazgul who were chasing him and his few companions. Pippin accompanies Gandalf and Faramir to a meeting with Denethor; Faramir reports about the events on the border, and about his meeting with Frodo. Denethor is displeased with his actions, and would prefer to have the Ring brought to his keeping. The next day Faramir leaves the City again to help in the defence of the passages across the Anduin. The defenders cannot withstand the well-prepared attack, however, and a day later survivors retreat back into the city, chased by the enemies; Faramir is brought in last, wounded by a poisoned dart. Huge numbers of enemies, led by the Captain of the Ringwraiths himself, encircle Minas Tirith and start a siege, digging trenches of fire and preparing great engines of war. Denethor is broken to see Faramir mortally wounded, and he gives up all hope and the defence of the city and retreats into the houses of the dead, intending to burn himself and Faramir. He releases Pippin of his service, and Pippin runs looking for Gandalf who might still prevent Denethor from committing some madness. Meanwhile the enemies attack the city gate with a huge ram, and break it open after several attempts. The Lord of the Nazgul rides in and is confronted by Gandalf alone; in that very moment, though, the horns of Rohan ring in the distance.
The host of Rohan rides quickly towards Gondor for four days. One night Merry listens to Théoden and Éomer talking to Ghân-buri-Ghân, a chieftain of the Wild Men of the nearby woods. Orcs seem to have waylaid the road towards Minas Tirith, and Ghân offers to show them a long-abandoned and unknown path through the forest. Thus they come unchallenged to the field of Gondor, for all the enemies are busy assailing the city walls. Just when the armies of Mordor are attacking the gates with their great ram, Théoden blows a signal with his horn and the Rohirrim charge into attack.
In the first onset, Théoden slays a chieftain of the Southrons. Then the Captain of the Ringwraiths, riding upon his terrible winged creature, descends near Théoden; his horse, driven mad with fear, falls on his side and buries the king underneath him. Only Éowyn, who was disguised as Dernhelm, stands beside him in this moment; Merry's courage finally awakens and he attacks the Ringwraith from behind, and Éowyn with her last strength slays the Wraith-king. Before dying Théoden says farewell to Merry, and greets Éomer as the new king. The remaining defenders of Minas Tirith issue from the City to help the Rohirrim; the Prince Imrahil meets the men carrying Théoden and Éowyn, and notices that she is still alive, and sends for the healers. The forces of Rohan and Gondor are slowly losing the battle with the huge armies of the Enemy. But then a fleet of ships of Umbar sails up the Anduin, at to the surprise of both the attackers and the defenders it is not bearing the Corsairs, enemies of Gondor, but Aragorn and his company, as well as the hosts of southern Gondor. Now the battle turns to the favour of the West, and by the end of the day no enemies remain alive on the field.
Pippin finds Gandalf and brings him to the Houses of the Dead to prevent Denethor from burning himself and Faramir alive. There they find Beregond (whom Pippin had warned of Denethor's madness) fighting Denethor's servants. Gandalf tries to convince Denethor that the hour and way of one's death are not one's own to choose, and that his duty is to lead the defence of the City; but Denethor firmly believes that the might of Mordor is too great now and everything is hopeless. Beregond prevents him from slaying Faramir; then Denethor grabs a torch and throws it into the pile of wood prepared there, and throws himself upon it, and burns. It seems that a palantír, kept secretly in the White Tower, was the origin of his dismay, for he had looked in it often and seen nothing but the gathering of the great armies of Mordor. Then they take Faramir to the Houses of Healing, though it is uncertain whether he will ever awake again.
Merry, who has, totally exhausted, followed the bearers of Théoden's body but went astray, is finally found by Pippin and taken to the Houses of Healing. There Gandalf hears an old woman mention a legend that the hands of a king are the hands of a healer; and he goes looking for Aragorn, who might still have that skill. Aragorn decides not to claim his kingship until the war with Mordor is over, but he does come to help the wounded. First he tends Faramir, Éowyn and Merry. Faramir was struck by a poisoned arrow, but most of all he was affected by the "black breath" of the Nazgul; and Éowyn and Merry were falling into darkness after confronting the Ringwraith. Aragorn heals them with a herb called athelas, and they wake up, though they will still have to rest for several days. He and the sons of Elrond labour in the Houses of Healing until the morning hours.
The next morning Legolas and Gimli enter the City and meet with the Prince Imrahil; then they visit Merry and Pippin in the Houses of Healing. They talk about the passing of the Paths of the Dead: how they rode for several days, and Aragorn called upon the shades of the Dead to fight for him, how they captured the fleet of Umbar in Pelargir, and how they sailed up the Anduin to join the battle of the Pelennor fields. Meanwhile there is a meeting of the captains: Gandalf, Aragorn, Imrahil, Éomer, and the sons of Elrond. Gandalf presents his plan to ride towards the Black Gate of Mordor, as if to challenge battle with Sauron, such that he would empty Mordor and turn all his attention towards them; this would increase Frodo's chances to reach Orodruin and destroy the Ring. For so long as the Ring still exists, Sauron's strength is too great to be conquered in war. The plan is accepted, and a host of seven thousand men is to depart in two days' time.
The host of the West marches towards the Gates of Mordor, and several times every day the heralds proclaim the coming of the King and challenge the forces of Mordor. Some men are left as guard at the Cross-roads, and later on some grow afraid and turn back. Nobody answers the challenges, though, except for a small host of Orcs and Easterlings that they defeat easily. At length the army comes before the Black Gate of Mordor, and again challenge Sauron to come out and make amends for his evil deeds. An embassy issues out then, led by the Mouth of Sauron, an evil man who had entered the service of Sauron and become the Lieutenant of the Dark Tower and a mighty sorcerer. The Mouth declares that a halfling-spy was captured (and shows Frodo's gear) and demands that the Captains of the West should yield to Sauron's territorial demands or the spy will be brutally tortured. Gandalf refuses the terms, but takes Frodo's items; then the embassy, in rage and fear, turns back towards the gate. Finally Sauron releases his trap: the gates swing wide open and an army pours out, several times outnumbering the host of the West. In this last, desperate defence, Pippin slays a great hill-troll, but then falls unconscious himself.