Frodo has finally decided to head to Mordor on his own because the Ring is working its dark magic on his buddies. Frodo's trusty companion Sam refuses to let Frodo go it alone, so the two hobbits head to Mordor together.
Aragorn, meanwhile, finds Boromir dying, and learns that the orcs have taken Merry and Pippin. Not good. Legolas, Gimli, and Aragorn resolve to chase after the orcs that stole Merry and Pippin, to honor the remaining members of the fellowship. These are stand-up dudes.
After four days of running, Aragorn & Co. bump into a band of Riders of Rohan. After a brief exchange of news—Boromir and Gandalf have died, Théoden seems a little out of sorts, and Saruman is building power in Rohan—Aragorn, Legolas, and Gimli continue to track the hobbits to the edge of the ancient Forest of Fangorn.
Meanwhile, Merry and Pippin are being hauled around by a bunch of bickering orcs. As the orcs spot Riders of Rohan in the distance, they stow Merry and Pippin at the outskirts of the Forest of Fangorn for safekeeping and engage in battle with the Riders, who outfight them, killing every last orc, and allowing Merry and Pippin to crawl off into the forest.
There, the two hobbits run into Treebeard, who is an Ent, or tree-herder. It turns out the orcs have been abusing the forest that is in his care, under the orders of Saruman. Treebeard thinks it's time for the Ents to step in, and he hopes to convince them to make a last stand against Isengard.
As Aragorn follows Merry and Pippin's trail, he is interrupted by an old man approaching the three soundlessly. The man throws off his cloak and (against all odds) it's Gandalf. He's shining and white, and more importantly, back from the dead. Gandalf tells his old buddies that Merry and Pippin have been rescued by the Ents of Fangorn. Sweet. Now that Merry and Pippin are safe, Gandalf tells them, they have to ride to Edoras to see a bloke named Théoden.
Aragorn, Legolas, Gimli, and Gandalf arrive at Edoras, where Théoden, King of Rohan, is under the control of his double-crossing, totally disgusting counselor Gríma Wormtongue. Assessing the situation, Gandalf quickly sends up a flash of light out of his staff, and Wormtongue sprawls on the floor at his feet. Problem solved. Théoden's head now clear, he promptly boots Wormtongue, who has been working for Saruman, out of the kingdom. It's time for Théoden to ride to Helm's Deep, to fight off Saruman's approaching army.
At the River Isen, Gandalf ditches the Rohan folks, promising he'll meet up with them at Helm's Deep the next morning. Once Aragorn, Legolas, Gimli, and the soldiers of Rohan arrive at Helm's Deep, the battle ensues, and things are not looking good for the human folk. They are totally outnumbered by evil orcs. At dawn, when Aragorn stands at the gates of Helm's Deep and demands that the orcs leave, they laugh. But they seem frightened, too, and soon we find out why: Gandalf's reinforcements have arrived, and with their help, the orcs are soon defeated.
After the victorious battle, Gandalf suggests that Théoden tag along to Isengard. When they arrive, they find the walls around Isengard torn down, and the land around the tower of Orthanc flooded. Sitting among the ruins are Merry and Pippin. They announce that Saruman is trapped inside the tower with Gríma Wormtongue. Treebeard is in charge of Isengard now. Gimli, Legolas, and Aragorn are overjoyed to see their hobbit companions safe and sound. Apparently the Ents swarmed over Isengard, pulling down its gates and flooding the land. Go trees.
Despite this victory, it's all the more urgent that all available fighters make their way to Gondor, to defend it against Sauron, who is sure to attack soon. Gandalf takes Pippin, hops on his horse Shadowfax, and rides hard to Minas Tirith. Théoden, Aragorn, and the Riders of Rohan will follow soon after.
Now we get back to the other half of the battle against Sauron: the Ring quest. On their journey, Frodo and Sam confront Gollum (who has been following them), and make him swear to help them get to the Black Gate of Mordor. Sam, meanwhile, has noticed that Frodo seems more and more affected by the Ring. He's also suspicious of Gollum, who seems torn; his better half wants to help Frodo, while his worse half wants to lead Frodo and Sam to Her. Uh, who?
Finally, they reach the Black Gate, but just when Frodo works up his courage to approach, Gollum grabs him and insists that they go another way, through the land of Ithilien, and then up a long stair through the pass of Cirith Ungol. In Ithilien, they run into some human scouts and Gollum disappears.
The scouts are men of Gondor, and Frodo starts telling his story to Captain Faramir, their leader. Faramir pulls Frodo and Sam aside, for a secret chat about "Isildur's Bane," and then he makes some uncomfortably close guesses about Frodo's mission. He insists that he would never take the Ring from Frodo, and promises to do his best to help Frodo in his quest.
That night, Gollum reappears, having found Faramir's secret hideout. Frodo asks Faramir to have mercy on Gollum, and Faramir reluctantly agrees. He ties Gollum up instead. But Gollum is not a happy camper, and blames Frodo for his current state. Frodo explains to Faramir that Gollum is leading them into Mordor to help their mission.
Against Faramir's warnings, Frodo, Sam, and Gollum leave in the direction of Cirith Ungol. Though Sam is sure that Gollum is planning something, the trio continues up a series of stairs that lead high up in the mountains. Gollum, having reverted to his wicked self, shows them to a cave in the side of the mountain, insisting that it's the only way into Mordor. No surprise here, folks: it's a trap. There's a giant, hungry spider named Shelob (oh, so that's the "Her") waiting inside. Shmoop's Worst Nightmare.
Frodo fends off Shelob at first, but without the help of Sam (who is busy fighting Gollum), he is overcome by the spider. Sam kills Shelob, but it's too late. Frodo, wrapped in spider silk (shudder) appears to be cold and dead. Sam resolves to go on as best he can.
He takes the Ring from Frodo, and then he lays Frodo out gently, as though for burial. As he stumbles off, he hears orcs chattering about Shelob and the little fellow who worships her (Gollum). Then he hears something really horrible. Frodo isn't dead—just paralyzed. Sam sees the orcs grab Frodo and carry him to their tower as a prisoner. Poor Sam is out there on his own, but he resolves to save Frodo, whatever the cost.