On the second day of their journey, a messenger who tells them that Saruman has almost won meets the group. Gandalf leaves them with the excuse of having an errand to run. When they reach Helm's Deep, the battle is fierce and the orcs seem to be winning. Suddenly Theoden and his men ride up from behind, trapping the Orcs. Gandalf appears with a contingent of reinforcements. The orcs flee into the forest, but the trees capture them and the battle is over as quickly as it began.
Gandalf's strategy proves victorious. He had ridden away to gather men for reinforcements. Many heroes are proclaimed that day, but none as precious as Gandalf. Once again the forces of evil have been overthrown by those of good.
King Theoden, Gandalf the white rider, Aragorn, Legolas, Erkenbrand, Eomer, Gimli and the men of Rohan all gather beside a stream. When Theoden asks Gandalf about his wizardry over the trees, Gandalf laughs and tells them that it has not been his doing. He asks them to come with him to Isengard if they wish to know more about the trees.
After resting, the men set forth again. They come to Orthanc, the citadel of Saruman at Isengard. They are surprised to find that Treebeard and his Ents have destroyed the citadel, and that Saruman and Wormtongue have hidden themselves away, guarded by none other than Merry and Pippin. Theoden, who is anxious to see Treebeard, says good-bye to the hobbits and accompanies Gandalf to the Northern wall.
At last the band of travelers, minus Frodo, are complete.
Merry and Pippin tell their companions how they came to be at Isengard after escaping the orcs and being helped by Ents. Merry tells them how the whole forest marched to Isengard and tore up the gates. Pippin then tells them how Saruman almost managed to escape but was spotted in time and took refuge in the stronghold of Orthanc that even the iron tearing Ents could not destroy. He also tells them how Gandalf came by and asked for Treebeard's help, which he gave. Pippin tells them how Wormtongue came to give Saruman a message, but seeing the destruction he wanted to leave. At that point Treebeard captured him and that is how he came to be cloistered with Saruman.
Again, Tolkien takes the time to backtrack and explain the missing pieces of the plot that the narrative has not revealed.
Gandalf warns everyone about Saruman's voice, which has powers beyond their imagination. Theoden, Aragorn, Legolas and Gimli decide to go with Gandalf to get a first hand view of Saruman. When Saruman does appear, his voice sounds like the sweetest anyone has ever heard. He speaks to Theoden and tries to persuade him to be his friend. Gandalf doesn't say a word because he has to let Theoden make his own choices: either succumb to Saruman's wizardry or fight it. Gimli is not taken in and neither is Eomer. Eventually Theoden is able to control himself and he rejects Saruman's appeal.
Theoden's men have fallen under Saruman's spell and are confused by their leader's rejection. Saruman is angered and when his voice changes the men realize their mistake in falling for his tricks. Gandalf gives Saruman a chance to discard his evil ways, but Saruman not only does not take Gandalf's offer, he even tries to persuade Gandalf to join him. When Gandalf asks him once more to come out of Orthanc, Saruman turns away. Gandalf raises his hand and commands Saruman's staff to break. Saruman's staff breaks and he falls back. At that Wormtongue hurls an object at Gandalf but misses and Pippin picks it up. Gandalf retrieves it, recognizing it at once as a palantir (a seeing stone). Gandalf knows that though Saruman is a lost cause, this is a great treasure.
Gandalf asks Treebeard to pour back the water into Orthanc so that Saruman can never escape. Treebeard agrees.
In this scene, Gandalf again asserts his wisdom and incorruptibility. He also takes over as leader of the wizards, having been unable to persuade Sarumon to repent his wicked ways. Gandalf emerges greater and more admirable. Good once again defeats evil. And order is semi-restored.