When Auden impulsively goes to stay with her father, stepmother, and new baby sister the summer before she starts college, all the trauma of her parents' divorce is revived, even as she is making new friends and having new experiences such as learning to ride a bike and dating.

One Sunday afternoon in Southern California, Bert Cousins shows up at Franny Keating's christening party uninvited. Before evening falls, he has kissed Franny's mother, Beverly-thus setting in motion the dissolution of their marriages and the joining of two families. Spanning five decades, Commonwealth explores how this chance encounter reverberates through the lives of the four parents and six children involved. Spending summers together in Virginia,...