The Lord of the Rings
Frodo and Sam are in the Emyn Muil mountains and journey eastwards to Mordor. While they are still in the Emyn Muil, they are attacked by Gollum. But the hobbits can defeat and catch him. Gollum has to promise to show them the way into Mordor. They go through the Dead Marshes and come to the Morannon, the Black Gate of Mordor. They cannot go in, but Gollum says he knows a secret way into Mordor.