Thousands of years before the events of the novel, the Dark Lord Sauron had forged the One Ring to rule the other Rings of Power and corrupt those who wear them: the leaders of Men, Elves and Dwarves. He was later vanquished in battle by an alliance of Elves and Men led by Elendil and Gil-galad. Isildur, a ruler of Men, cut the One Ring from Sauron's finger, claiming it as an heirloom for his line, and Sauron lost his physical form. When Isildur was later ambushed and killed by Orcs, the Ring was lost in the River Anduin at Gladden Fields.
Over two thousand years later, the Ring was found by one of the river-folk called Déagol. His friend Sméagol immediately fell under the Ring's influence and strangled Déagol to acquire it. Sméagol was banished and hid under the Misty Mountains, where the Ring extended his lifespan and transformed him over the course of hundreds of years into a twisted, corrupted creature called Gollum. He lost the Ring, his "precious", and, as recounted in The Hobbit, Bilbo Baggins found it. Meanwhile, Sauron re-assumed physical form and took back his old realm of Mordor. Gollum set out in search of the Ring, but was captured by Sauron, who learnt from him that "Baggins" in the Shire had taken it. Gollum was set loose, and Sauron, who needed the Ring to regain his full power, sent forth his powerful servants, the Nazgûl, to seize it.
The Fellowship of the Ring
The story begins in the Shire, where the Hobbit Frodo Baggins inherits the Ring from Bilbo Baggins, his cousin[note 2] and guardian. Neither is aware of its origin and nature, but Gandalf the Grey, a wizard and old friend of Bilbo, suspects the Ring's identity. When he becomes certain, he strongly advises Frodo to take it away from the Shire. Frodo leaves, accompanied by his gardener and friend, Samwise ("Sam") Gamgee, and two cousins, Meriadoc ("Merry") Brandybuck and Peregrin ("Pippin") Took. They nearly encounter the Nazgûl while still in the Shire, but shake off pursuit by cutting through the Old Forest, where they are aided by the enigmatic Tom Bombadil, who alone is unaffected by the Ring's corrupting influence. After leaving the forest, they stop in the town of Bree where they meet Strider, who is later revealed to be Aragorn, Isildur's heir. He persuades them to take him on as guide and protector. They flee from Bree after narrowly escaping another assault, but the Nazgûl follow and attack them on the hill of Weathertop, wounding Frodo with a Morgul blade. Aragorn leads the hobbits toward the Elven refuge of Rivendell, while Frodo gradually succumbs to the wound. The Ringwraiths nearly overtake Frodo at the Ford of Bruinen, but flood waters summoned by Elrond, master of Rivendell, rise up and overwhelm them.
Frodo recovers in Rivendell under the care of Elrond. The Council of Elrond reveals much significant history about Sauron and the Ring, as well as the news that Sauron has corrupted Gandalf's fellow wizard, Saruman. The Council decides that the Ring must be destroyed, but that can only be done by returning it to the flames of Mount Doom in Mordor, where it was forged. Frodo volunteers to take on this daunting task, and a "Fellowship of the Ring" is formed to aid him: Sam, Merry, Pippin, Aragorn, Gandalf, Gimli the Dwarf, Legolas the Elf, and the Man Boromir, son of the Ruling Steward Denethor of the realm of Gondor.
After a failed attempt to cross the Misty Mountains via the Redhorn Pass across the flank of Caradhras, the company are forced to try a more perilous path through the Mines of Moria, where they are attacked by the Watcher in the Water before the gate. Inside, they discover the fate of Balin and his colony of Dwarves. After repulsing an attack, they are pursued by orcs and an ancient and powerful demonic creature called a Balrog. Gandalf confronts the Balrog, but in their struggle, both fall into a deep chasm. The others escape and take refuge in the Elven forest of Lothlórien, where they are counselled by Galadriel and Celeborn.
With boats and gifts from Galadriel, the company travel down the River Anduin to the hill of Amon Hen. Boromir succumbs to the lure of the Ring and attempts to take it from Frodo. Frodo escapes and determines to continue the quest alone, though Sam guesses his intent and comes along.
The Two Towers
Orcs sent by Saruman and Sauron kill Boromir and kidnap Merry and Pippin. After agonizing over which pair of hobbits to follow, Aragorn, Gimli and Legolas pursue the orcs bearing Merry and Pippin to Saruman. In the kingdom of Rohan, the orcs are slain by a company of the Rohirrim. Merry and Pippin escape into Fangorn Forest, where they are befriended by Treebeard, the oldest of the tree-like Ents. Aragorn, Gimli and Legolas track the hobbits to Fangorn, and encounter Gandalf, resurrected as the significantly more powerful "Gandalf the White" after his mutually fatal duel with the Balrog. Gandalf assures them that Merry and Pippin are safe. They then ride to Edoras, the capital of Rohan, where they free Théoden, King of Rohan, from the influence of Saruman's henchman Gríma Wormtongue. Théoden musters his fighting strength and rides to the ancient fortress of Helm's Deep, but en route Gandalf leaves to seek help from Treebeard.
Meanwhile, the Ents, roused from their customarily peaceful ways by Merry and Pippin, attack Isengard, Saruman's stronghold, and trap the wizard in the tower of Orthanc. Gandalf convinces Treebeard to send an army of Huorns to Théoden's aid. Gandalf and Rohirrim reinforcements arrive at Helm's Deep just in time to defeat and scatter Saruman's army. The Huorns dispose of the fleeing orcs. Gandalf then parleys with Saruman at Orthanc. When Saruman rejects his offer of redemption, Gandalf strips him of his rank and most of his powers. Pippin looks into a palantír, a seeing-stone that Saruman had used to communicate with Sauron and through which he was ensnared. Gandalf rides for Minas Tirith, chief city of Gondor, taking Pippin with him.
Frodo and Sam capture Gollum, who had been following them from Moria, and force him to guide them to Mordor. Finding Mordor's Black Gate too well guarded to attempt, they travel instead to a secret passage Gollum knows. Torn between his loyalty to Frodo and his desire for the Ring, Gollum eventually betrays Frodo by leading him to the great spider Shelob in the tunnels of Cirith Ungol. Frodo is felled by Shelob's sting, but Sam fights her off. Sam takes the Ring and leaves Frodo, believing him to be dead. When orcs find Frodo, Sam overhears them say that Frodo is only unconscious, and chases after them.
The Return of the King
Sauron unleashes a heavy assault upon Gondor. Gandalf arrives at Minas Tirith to alert Denethor of the impending attack. The city is besieged, and Denethor, deceived by Sauron, gives up hope and commits suicide, nearly taking his remaining son Faramir with him. Aragorn feels he has no choice but to take the Paths of the Dead in order to reach Gondor in time, accompanied by Legolas, Gimli and the Dúnedain Rangers from the North. There Aragorn raises an undead army of oath-breakers bound by an ancient curse that said they could not rest until they had fulfilled their vow to the king of Gondor. The ghostly army helps them to defeat the Corsairs of Umbar who are invading southern Gondor. Commandeering the ships of the Corsairs, Aragorn leads reinforcements up the Anduin to relieve the siege of Minas Tirith, and the forces of Gondor and Rohan defeat Sauron's army in the Battle of the Pelennor Fields.
Meanwhile, Sam rescues Frodo from the tower of Cirith Ungol, and they set out across Mordor. In order to distract Sauron from his true danger, Aragorn leads the armies of Gondor and Rohan in a march on the Black Gate of Mordor. His vastly outnumbered troops fight desperately against Sauron's forces. Reaching the edge of the Cracks of Doom, Frodo is unable to resist the Ring any longer, and suddenly and fiercely claims it for himself. But Gollum suddenly reappears, struggles with Frodo and bites off his finger, Ring and all. Celebrating wildly, Gollum accidentally falls into the fire, taking the Ring with him; and so Frodo's mission is completed. With the destruction of the One Ring, Sauron is permanently shorn of his power, the Nazgûl perish, and his armies are thrown into such disarray that Aragorn's forces emerge victorious.
With the end of the War of the Ring, Aragorn is crowned Elessar, King of Arnor and Gondor, and marries his long-time love, Arwen, daughter of Elrond. Saruman escapes from Isengard and, seeking to carve out a new kingdom, enslaves the Shire. The four hobbits, upon returning home, raise a rebellion and overthrow him. Gríma turns on Saruman and kills him in front of Frodo's house, and is slain in turn by hobbit archers. The War of the Ring thus comes to its true end on Frodo's very doorstep.
Merry and Pippin are acclaimed heroes, while Sam marries Rosie Cotton and uses his gifts from Galadriel to help heal the Shire. Frodo, however, remains wounded in body and spirit after having borne the oppressive weight of the One Ring so long.
Several years later, accompanied by Bilbo and Gandalf, he sails from the Grey Havens west over the Sea to the Undying Lands to find peace. After Rosie's death, Sam gives his daughter the Red Book of Westmarch, containing the account of Bilbo's adventures and the War of the Ring as witnessed by the hobbits. Sam is then said to have crossed west over the Sea himself, the last of the Ring-bearers.