For what major change is Evvie preparing when the reader first meets her in the prologue entitled, First?

When the prologue opens, Evvie is packing a suitcase, loading it into her car, and preparing to grab a few more of her belongings from the house she shares with her husband Tim. Evvie has decided to leave her husband and she is preparing to do so. By leaving before her husband returns from his shift as a physician, Evvie hopes to avoid a confrontation with Tim.