In the film The Lord of the Rings : The Return of the King , Frodo leaves Sam behind before they arrive at the tunnel leading to Mordor .
Frodo tells Sam to go home , before Frodo and Gollum continue to the tunnel leading to Mordor , where Gollum tricks him into venturing into the lair of the giant spider Shelob .
The Lord of the Rings-COLON- The Return of the King