Complex sentence: Ryan pretends to be a staunch nationalist--in an early scene, he strongly supports the recently suppressed Easter Rising, referring to the rebels as "our boys"--but in truth he is an informer for the British.
Split into simpler sentences: Ryan pretends to be a staunch nationalist; in an early scene, he strongly supports the recently suppressed Easter Rising, referring to the rebels as "our boys". But in truth he is an informer for the British.