Gandalf’s group rides south of the River Isen. Legolas sees shapes moving in the distance, but he is unable to distinguish them clearly. The next day, Gandalf becomes alarmed, and with a word to his trusty horse, Shadowfax, speeds off, ordering the group to proceed to Helm’s Deep and to stay far from the plains of Isen.
Obeying Gandalf without knowing his reasoning, the group goes to the Deep, a narrow gorge in the mountains on the far side of the Westfold Vale. Théoden reveals that Saruman knows the region very well, and he foresees that there will be a great battle between the Orcs and the armies of Rohan. Théoden and his Riders arrive at the Deeping Wall, a great fortification near Helm’s Deep. They do not have enough provisions for a long encampment, having prepared for a quick battle rather than a long siege.
Suddenly, the battle begins with a great thunder, as the area around the Deeping Wall is flooded with Orcs. Many arrows are launched on both sides, and Legolas and Gimli fight valiantly. After many hours, the forces of Rohan grow tired. Aragorn is worried to see that the Orcs have crept beneath the Wall and have lit a flaming trail of Orc-liquor below the Riders. Aragorn goes into the Hornburg, the nearby citadel, to find that Éomer has not arrived. Aragorn learns that the Orcs have used their flaming liquid to blast through the Wall and seize it. Aragorn feels demoralized even though he is told that the Hornburg has never once been taken. The Orcs jeer at the Riders in the citadel, telling them to come out and meet their fate at the hands of the Uruk-hai. Suddenly, the roar of trumpets is heard, and King Théoden appears in martial splendor. The Orcs, gripped with fear, begin to retreat, dispersing throughout the land surrounding Helm’s Deep. The Hornburg yet again remains safe. Suddenly, a horseman clad in white appears in the distance. The Riders of Rohan hail Gandalf, the White Rider, on the back of Shadowfax.
Éomer, Théoden, Gandalf, Gimli, Legolas, and Aragorn all gather on the plain near Helm’s Deep after the victory over the Orcs. Éomer expresses wonder that Gandalf came at just the right time. Though the men are weary from battle, Gandalf urges the King to assemble a party to ride with him to Isengard to meet Saruman. Théoden chooses Éomer and twenty Riders to accompany them. Gandalf rides in the company of Aragorn, Legolas, and Gimli. They sleep in preparation for the journey the next day. The slain Orcs are gathered on the fields.
The party sets out for Isengard the next day, passing through a forest of strange trees along the way. Gimli praises the beauty of caves to Legolas, who prefers the woods. Legolas is surprised to see eyes among the trees, and Gandalf explains that the forest is full of Ents, who are not enemies. The Riders of Rohan grieve over their slain fellow warriors, whose bodies litter the fields around them. Eventually, they reach the Misty Mountains. They sense that the area known as Nan Curunír, or the Wizard’s Vale, is burning. They see a strange black liquid pass over the ground near them. Gandalf orders his men to ignore it and wait until it passes.
Riding on for several days, the group finally arrives at Saruman’s stronghold at Isengard. They see the great stone tower called Orthanc, where Saruman lies in wait, surrounded by a deep gorge on all sides. Once Isengard was abloom with gardens and orchards, but ever since it has been under Saruman’s control, it has been barren and desolate. At the gates of Isengard, Gandalf’s group is surprised to find Merry and Pippin lounging and smoking. It is the first time Théoden has ever seen Hobbits. After a brief chat, Merry and Pippin deliver the message that Fangorn is waiting to meet with Gandalf on the northern wall of Isengard. Gandalf sets out to meet the Ent, accompanied by Théoden.