Complex sentence: Madam Cassandra Hartz is very shrewd, but she runs Gotham's finest brothel in her luxury penthouse, frequented by who's-who in New York City; high-society figures, politicians, entertainment stars and the kingpins of crime.
Split into simpler sentences: Madam Cassandra Hartz is very shrewd but she runs Gotham's finest brothel in her luxury penthouse, frequented by who's-who in New York City. High-society figures, politicians, entertainment stars and the kingpins of crime.