The Riders of Rohan, with Gandalf and Co. in tow, head for Helm's Deep. The ford of the River Isen is about forty leagues (480 miles) from Edoras.
Try as he might, Legolas can't see far in front of them. There is some kind of magical power blocking him. The air is also growing heavier and heavier as they go along. This can't be good.
At the end of the second day, a lone horseman approaches named Ceorl. He asks for Éomer.
According to Ceorl, all the forces of Isengard are out doing mischief, and they're not just orcs. Saruman has also armed the "wild hillmen and herdfolk" (3.7.9) of Dunland.
All these forces have been bad news for Rohan. Erkenbrand of Westfold has gathered the troops who are left to his fortress in Helm's Deep, where they're waiting for the Edoras party to join them.
Sure thing, says Théoden, let's head to Helm's Deep to help. Gandalf agrees that that's the best course of action, so now it's Helm's Deep or bust.
Unfortunately, Gandalf has a bit too many irons in the fire at this point. The dude has got somewhere to be, so he parts ways with the riders, promising to meet up with them at Helm's Deep.
After riding through the night, they arrive at the fortress, which contains a central fort, called the Hornburg, surrounded by the outer Deeping Wall. It lies deep in the White Mountains, on the outer border of Rohan.
As they approach the fortress, they get some bad news from their scouts.
There are orcs and wild men on their way from Isengard to Helm's Deep. Uh oh. And to make matters worse, rumor has it that Erkenbrand never made it to Helm's Deep with his troops. Double uh oh.
Éomer advises that they get their butts in gear, so that they can arrive in the caverns of Helm's Deep before Saruman's reinforcements reach the orcs that have already arrived.
They ride hard, but Saruman's forces are close behind them, burning everything in their path as they go.
When the Rohan folks arrive at Helm's Deep, an old soldier, Gamling, welcomes them, assuring them that Helm's Deep has lots of supplies stored up. They're good to go for battle.
Even if the orcs are burning Rohan's fields, they will not have famine (so long as the soldiers at Helm's Deep survive this war, that is). Well hey, that's something.
Éomer sets his men to their posts.
Gimli, for one, is happy to be fighting once more on hard rock. He understands this terrain. And hey, he won't have to ride any more horses.
They wait out the night as hundreds and hundreds of Saruman's troops come pouring into the valley. Shmoop's guessing they're not feeling too confident.
The enemy pushes forward and the archers of Rohan get busy trying to push them back.
Aragorn and Éomer rush into battle at the Deeping Wall, fighting their way through the orcs back to the gates of the Hornburg. Take that, you evil jerks.
Éomer is almost killed until Gimli unexpectedly leaps in and saves him.
Legolas and Gimli fight tirelessly. These are definitely dudes you want on your team. They even have a competition going on total number of orcs slain. (Guess who's winning.)
The men of Rohan (plus Aragorn and Co.) fight through the day and night, but they are horribly outnumbered.
To make matters worse, some of Saruman's troops creep under the wall and use "the fire of Orthanc" (3.7.110) to blast a hole through which the orcs stream.
With Aragorn's strength, all the troops behind the wall who can make it back to the Hornburg do.
Inside the fortress, Aragorn finds Legolas, but not Gimli or Éomer.
Needless to say, things are not going well. Not well at all.
Even Théoden is starting to lose faith. Helm's Deep has never fallen to an enemy, but "how shall any tower withstand such numbers and such reckless hate?" (3.7.134). That's a really good question, Théo.
Here's an idea: Aragorn and Théoden decide to ride together around the edge of the Hornburg, keeping up morale and helping where they can.
Then, at dawn, Aragorn stands at the gates. He's flat out determined as he warns the orcs to leave. Helm's Deep has never been taken, and it's not about to happen this time either.
The orcs are frightened by his kingly air, but they still laugh and jeer. Oh, real mature, guys.
The orcs break through the gate where Aragorn is standing, and he runs back to the king's tower.
But just as the orcs have this great success, a horn rings out from behind them.
A horn also blasts out from the Deep, and Théoden King rides forth from the Hornburg with Aragorn at his side.
Suddenly, the orcs lose their nerve. In the light of the dawn, they see that the land itself has changed, and they are surrounded by a dense forest. There's some seriously powerful magic going on here.
Out of the forest comes "their final doom" (3.7.157). What's that, you ask?
Well, reinforcements have come from the hills: the White Rider, Gandalf, has come with Erkenbrand and a thousand soldiers on foot.
The hosts of Isengard are caught between Théoden in front of them and Erkenbrand behind. Those that manage to escape rush into the trees, but they disappear forever. This forest is not your average forest, it seems.
Oh, and the ever curious Legolas wants to go and look at these magic trees. But that'll have to wait, dude.