Lord of the Rings Walkthrough:
River Anduin: Aragorn and the Orcs

Talk to everyone. Aragorn has to go through orc lines. Note that your final battle is coming up with Aragorn so get lots of elven arrows and as much health as you can. Go through the lines carefully, using the super-charge attack whenever you can. You'll find a switch lever along the way. Get to the gate, use it and open the gate.

Now Gollum shows up. Listen to his rambling about presents and then chase him. You'll get a lembas for hitting him. Note if you don't, instead orcs will attack you immediately and you'll have to kill them.

Lord of the Rings Walkthrough