Complex sentence: At his funeral, Tessio, one of the Don's capos, approaches Michael to arrange a meeting between him and Don Barzini, unknowingly revealing his own treachery as Vito had forewarned.
Split into simpler sentences: At his funeral, Tessio, one of the Don's capos, approaches Michael to arrange a meeting between him and Don Barzini. Tessio has unknowingly revealed his own treachery as Vito had forewarned.