Complex sentence: Jace, Clary, and Alec leave to break Simon out of jail where Simon is kept and breaks both him and Samuel, Simon's roommate, out, only to discover that Samuel is actually Hodge.
Split into simpler sentences: Jace, Clary, and Alec leave to break Simon out of the jail where he is kept. They break out both Simon and Simon's cellmate, Samuel, only to discover that Samuel is actually Hodge.