Graham Obermann is an established biographer of the Post-Impressionists. He is married to Celia Prosper, a modernist painter well-regarded by critics and collectors. As Obermann organizes a birthday party for Celia, looking after all the details, he describes in a single day the odd Prosper family and his attraction to his novelist brother-in-law Karl. Several significant events test all the characters in this family saga with subplots of many generations, and a new generation making its mark.