Complex sentence: The hobbits begin climbing a precarious stair carved in the cliff face that will take them into Mordor via a'secret way'; having overheard Gollum's plot to regain the Ring, Sam keeps a suspicious eye on him.
Split into simpler sentences: The hobbits begin climbing a precarious stair carved in the cliff face that will take them into Mordor via a'secret way'. But having overheard Gollum's plot to regain the Ring, Sam keeps a suspicious eye on him.