Diana Colvin 21 rich and "the finest girl in the world " is engaged to marry Roger Osterman 27 very rich and "the finest young fellow in the world." With the help of a mystified waiter Diana's uncle (her lawyer and guardian) sets up a play within a play to make sure Diana knows what she is getting into: marriage to a supreme tightwad who can give away millions to charity but can't leave a tip. The action--full of high-jinks as well as a serious message--takes place in a fancy New York City hotel.