Complex sentence: He offers them aqueous martinis, which is simply water with a olive in it served in a fancy glass, and introduces them to his wife Esmé Squalor who is a very "in" person and the city's sixth most important financial adviser.
Split into simpler sentences: He offers them "aqueous martinis", which is simply water with a olive in it served in a fancy glass, and introduces them to his wife Esmé Squalor. She is a very "in" person and the city's sixth most important financial adviser.