Sam is firmly decided to rescue Frodo, and therefore he must find a way to get into the watch-tower on the pass, where Frodo has been taken. He hears sounds of fighting from the tower, two orcs are shot with arrows in an attempt to run away; apparently the two orc-companies are fighting over Frodo's belongings. The main entrance to the Tower is guarded by the Two Watchers, horrible creatures like statues filled with great malice, that do not move yet seem to be aware of things around them. Sam holds up the Phial of Galadriel, and succeeds to run through the gate. Almost all the orcs were killed in the fighting; a small orc meets Sam on a stairway, but runs away in fear. Sam follows him, and listens to a conversation between the orc and Shagrat, who (though wounded) seems to have also survived the fight. The two orcs start to quarrel, and Snaga, the small orc, escapes; Shagrat runs out to get some help. Sam searches for Frodo and starts to sing; he hears a reply to his song, followed by Snaga's voice. Frodo was kept in the topmost chamber, accessible only by a ladder through a trap-door. Sam goes up and attacks Snaga, who falls down the ladder and breaks his neck. Then Sam and Frodo prepare to depart; Sam brings some orc-gear for Frodo (whom the orcs stripped of everything). Using the Phial, they pass the Watchers again, but the creatures utter a horrible cry, replied by a Nazgul from the darkness above.
Sam and Frodo barely avoid being discovered and travel to the north for a few days. They are troubled by the lack of food and water, and the Ring is becoming an ever greater burden to Frodo. The plain below them is full of Sauron's armies, and Frodo intends attempting to cross it where it is narrower. Hidden behind a bush, they hear a conversation between two orcs and discover that Gollum is still following them; one night Sam sees him nosing about, as well. The plain is still packed with orcs, and the hobbits have no choice but to follow the road along the sheer ridge of the Morgai. There they are caught up by a group of small orcs, being driven by two large ones towards Udun where Sauron's armies are gathering. The slave-drivers believe them to be deserters, and force them to join the company. Luckily, however, when the host nears the narrow entrance to Udun, confusion and quarrelling break out among different orc-companies, and the hobbits succeed to slip away unnoticed.
The hobbits follow an orc-road for several days, travelling towards Mount Doom. Thus they can make much faster progress than straight across the barren country, filled with rocks and crevices; and there are a few water-tanks along the road. But at last they have to leave the road and turn directly towards the Mountain. To ease the journey, they leave behind all gear that they are not likely to need any more. They reach Orodruin in two more days, and they almost run out of food and water. The next day they should ascend the Mountain, but Sam has to carry Frodo, who (tormented by the growing burden of the Ring) is completely exhausted. Near the summit they are attacked by Gollum, yet he is also weakened by hunger and Frodo escapes towards the Sammath Naur, the Chambers of Fire. Gollum begs Sam (who is still armed with Sting) for mercy, and Sam bids him be off. In the Chambers, however, Frodo is finally overcome by the power of the Ring and claims it for his own. Gollum creeps in and attacks him again, and bites off his ring-finger; then, in joy over regaining his Precious, he falls into the pit. Frodo, now delivered of his pain, and Sam come out and see that realm of Sauron is collapsing.
The battle of the Captains of the West and the hosts of Mordor is joined by the Eagles, led by Gwaihir their lord. In that very moment the Ring falls into the fire of Orodruin: the Black Gate collapses, the spirit of Sauron is destroyed, and the forces of Mordor, bereft of the Power that controlled them, dismay and many run away or beg for mercy. Gwaihir, accompanied by two other eagles, bears Gandalf towards Mount Doom, where they rescue Frodo and Sam. The two hobbits awake several days later and are greatly honoured by the host of the West on the field of Cormallen in Ithilien. They stay in Ithilien for many happy days, exchanging tales of their adventures with their friends, until at last the entire host boards ships and sails to Gondor.
Meanwhile Éowyn and Faramir are still in the Houses of Healing, recovering from their hurts. Éowyn is unhappy because she must spend her time in idleness, and desires a glorious death in battle (she also desired the love of Aragorn, but received from him nothing but pity and understanding). She meets Faramir (who, despite also being strong and valorous, is patiently waiting to be healed). The Eagles bring news of victory. Faramir and Éowyn spend a lot of time together, and eventually fall in love, and thus Éowyn is healed. - The host of the West returns to the City and Aragorn is crowned as the King Elessar. He declares that Faramir will be given Ithilien as a princedom, and he and his heir will remain Stewards. The companions spend many days in Minas Tirith, and it seems that Aragorn is still waiting for some kind of signal. One day he and Gandalf ascend a mountain-path and there, in an old hallow of the kings, find a sapling of the White Tree, which is planted in the court of the king. A few days later, a great company of Elves arrives from the North, including Galadriel, Elrond, and Arwen. Elrond gives to Aragorn the Sceptre of Annúminas, and Aragorn weds Arwen on the day of Midsummer.
Arwen gives Frodo permission to go to the Grey Havens instead of her, for by marrying Aragorn she chose to be mortal. Éomer and Gimli settle their argument over the beauty of Galadriel. At last a great company departs from Minas Tirith, bearing the body of King Théoden to Rohan. After the burial Éomer announces the wedding of Faramir and Éowyn. Then they go to Isengard, and there meet with Treebeard. Gimli and Legolas visit the Glittering Caves of Helm's Deep and the forest of Fangorn, and part from the company, turning towards their homes in the North. A little later Aragorn leaves them as well, going back towards Minas Tirith. The rest of the company travel on and overtake Saruman (who is now wandering around as a beggar, accompanied by Gríma). The folk of Lórien leave the company in Eregion, near the gates of Moria. Now the travellers turn towards Rivendell, and there the hobbits meet Bilbo and spend many days with him. Finally they decide to return home to the Shire, and to their joy Gandalf also decides to go with them, at least as far as Bree.
Frodo feels pain again in his shoulder, for it is a year since he was wounded. Yet it quickly passes, and after a few more days they reach Bree. They are warmly accepted by old Butterbur, and talk with him for a long time, telling about their doings and adventures. Barliman mentions that business has been bad, with many strangers and evil creatures lurking about; and he is glad to hear the news that the King has been restored. Bill the pony had also returned to Bree, and is now returned to Sam. The company stays in the inn for two nights, and then leave towards the Shire. Gandalf leaves the hobbits, for he intends to visit Tom Bombadil; and to the hobbits he advises to hurry, hinting that things might be amiss in the Shire.
The four hobbits come to the Shire, and find that much indeed has changed: the Brandywine Bridge is guarded by several Shirriffs, who deny them the entrance. It seems that Lotho Baggins has taken over in the Shire, calling himself "the Chief" and enforcing a long number of unfair Rules. The Shire is full of ruffians (there's Bill Ferny at the Bridge), many of them being squint-eyed Isengarders; and there has been much burning and senseless destruction. The travellers break in (against the Rules) and spend a night in the Shirriff-house; next day they encounter a group of Shirriffs in Frogmorton and a group of ruffians in Hobbiton, but both fail to arrest them, being surprised and frightened to meet four fearless and well-armed hobbits. The hobbits, with the help of Farmer Cotton, start an uprising against the oppressors; first a small group of ruffians attempts to calm down the rebellion, but outnumbered by the hobbits they give themselves in. Pippin brings a large number of Tooks and together they deal with the next attack of the majority of the ruffians. Then a group of hobbits, led by Frodo and his friends, go to Bag End to find Lotho. Instead they find Saruman, who has been the organiser behind all the trouble; they tell him to leave, and Wormtongue (who seems to have murdered Lotho at Saruman's command) in wrath and despair stabs him and is then shot by three hobbit-bowmen. This also marks the end of the War of the Ring.
These turbulent events are followed by a splendid, prosperous and happy year. The whole Shire is busy repairing the harms done by Saruman's ruffians. Sam remembers Galadriel's gift and discovers that the box contains a strange dust and a single silver seed. He uses the dust to plant trees all over the Shire where they had been hewn down by the ruffians, and he plants the silver nut in the Party Field in Hobbiton; and out of it grows a beautiful mallorn. Sam marries Rose Cotton; Frodo moves back to Bag End, and Sam and Rose come to live there as well. The next year their first daughter, Elanor, is born. On the anniversaries of the events at Weathertop and Cirith Ungol Frodo's old wounds hurt him again. In September, as Bilbo's birthday is approaching, Frodo and Sam set out again (towards Rivendell, as Sam thinks; though he does not intend to go all the way). Yet in the woods of the Shire they meet a large number of Elves, including Elrond and Galadriel; Bilbo is among them as well. Finally Sam realizes that Frodo intends to go to the Grey Havens, to pass over the Sea with the Elves and Bilbo. In the Havens Círdan the Shipwright and Gandalf await them; Gandalf, too, will board the ship. He has brought Pippin and Merry along as well, such that Sam will not be alone on the way home. Thus the elven-ship leaves Middle-earth; and the three hobbits return to the Shire.