The Two Towers opens with the disintegration of the Fellowship, as Merry and Pippin are taken captive by Orcs after the death of Boromir in battle. The Orcs, having heard a prophecy that a Hobbit will bear a Ring that gives universal power to its owner, wrongly think that Merry and Pippin are the Ring-bearers.
Several other members of the Fellowship, including Gimli, Legolas, and Aragorn, resolve to pursue Merry and Pippin. They follow the hobbits’ tracks through fields and forests, always on the lookout for Orcs. The group encounters the Riders of Rohan, led by Éomer.
Meanwhile, Merry and Pippin are being conveyed back to Orc headquarters when Orcs from another tribe, the Uruk-hai, kidnap them in pursuit of the Ring they believe the hobbits to be carrying. Pippin and Merry escape the Orcs and travel through the forest near the Entwash River, where an Ent (a giant treelike creature) named Fangorn befriends them. Fangorn offers the hobbits nourishment and conveys them to an Ent assembly. There, the Ents resolve to go to war against the Orcs of Isengard (creatures controlled by the corrupted wizard Saruman), who have been cruel to them.
Meanwhile, Saruman haunts Aragorn and his group as they travel the forest. Gandalf then appears to them, reborn after his earlier death in The Fellowship of the Ring as Gandalf the White, also known as the White Rider. Gandalf guides Aragorn’s group to Edoras, the Golden Hall of King Théoden. There, Gandalf exposes Théoden’s counselor, Wormtongue, as a spy for the evil Saruman. Gandalf also facilitates a reunion between Théoden and Éomer.
The group then proceeds to confront Saruman at Isengard, where they are surprised to find Merry and Pippin at the gates of Saruman’s headquarters. The hobbits tell Gandalf that the Ents wish to meet with him, to offer their aid in the struggle against Saruman. The group finds Wormtongue in Saruman’s tower, Orthanc. Wormtongue tries to kill Gandalf by throwing an object down on him from a window. That object is a palantír, a magic seeing-stone that transmits images. Pippin looks into the palantír, which allows the Dark Lord Sauron to discover where Pippin is and pursue him.
The second half of The Two Towers rejoins Frodo and Sam just after they separate from the rest of the Fellowship and begin making their way to Mordor to destroy the Ring. As they travel, they meet the creature Gollum, whom they tame and force to be their guide to Mordor. Sam and Frodo are wary of Gollum—they know he owned the Ring before and wishes to regain it—but they desperately need someone to direct them to their destination.
Frodo, Sam, and Gollum journey through a smelly marshland in which they can see the faces of slain warriors haunting the waters. They travel by night, as Gollum cannot stand the sun, so they are cold and hungry most of the time. They finally reach the Black Gate of the realm of Mordor and see Sauron’s Dark Tower rising overhead. The Gate is well guarded, and the hobbits wonder how they will be able to get inside. Gollum directs them to a different, hidden path into Mordor, where the guards will likely be sparser. On the way, the hobbits are frightened by dark shapes flying overhead—the Nazgûl, the Black Riders of Sauron who are searching for the Ring.
Along the way, Frodo meets a band of Men led by Faramir, the younger brother of Boromir. The men are suspicious of the hobbits at first, believing they are responsible for Boromir’s death. Frodo avoids telling Faramir that his brother betrayed the Fellowship by attempting to seize the Ring for himself, but Sam blurts it out. Faramir is shocked, but grateful to learn the truth, so he offers support to the hobbits’ journey. Faramir’s men nearly kill Gollum, who is caught as an intruder, but Frodo intercedes to save the creature.
Gollum leads Frodo and Sam up the mountain called Cirith Ungol and into tunnels inhabited by Shelob, a giant, deadly female spider. Shelob paralyzes Frodo with her sting, but Sam kills the spider. Frodo and Sam are separated, however, as Orc guards find Frodo and proceed to take him off to their headquarters, where they plan to search him for the Ring. Sam believes Frodo to be dead, so he accepts the responsibility of carrying the Ring by himself.
Surrounded by Orcs, the terrified Sam dons the Ring and finds that it enables him to understand the Orc language. Sam follows the guards who carry off the paralyzed Frodo. Upon hearing them mention that Shelob only devours living creatures, Sam is shocked to realize that his friend is alive. He chastises himself for taking the Ring for himself, unaware that he has actually saved the Ring and kept it from Sauron by taking it from Frodo. Sam realizes that Frodo is alive at the very moment when the guards enter Mordor, slamming the gates in Sam’s face. As The Two Towers ends, Sam is anguished by the thought that he and Frodo are separated.