While I Was Gone by Sue Miller
Thirty years ago Jo Becker's bohemian life ended when she found her best friend brutally murdered in the house they shared in Cambridge. Now Jo has everything: work she loves, a devoted husband, three grown daughters, and a beautiful home. But when an old friend settles in her small town, the fabric of her life begins to unravel and Jo hesitantly enters a relationship that returns her to the darkest moments of her past, imperiling all that she loves.