Complex sentence: The relatively provincial Klute becomes drawn into Bree's seedy world, discovers several of Bree's fellow call-girls have been murdered by a "john", and that she was nearly killed by the same man, presumably Gruneman.
Split into simpler sentences: The relatively provincial Klute becomes drawn into Bree's seedy world. He discovers that several of Bree's fellow call-girls have been murdered by a "john", and that she was nearly killed by the same man, presumably Gruneman.