Complex sentence: At one point, Cavender tries to change the bus Agnes is riding on into a convertible with a chauffeur, however he goofed twice, so they decided to get back to the bus, causing the bus driver to resign.
Split into simpler sentences: At one point, Cavender tries to change the bus in which Agnes is riding into a convertible with a chauffeur. However, Cavender makes errors twice, so they decided to get back to the bus, causing the bus driver to resign.