Killers of a certain age - Deanna Raybourn

They've spent their lives as assassins in a clandestine international organization, but at 60 years old, four women find they can't just retire - it's kill or be killed in this book by New York Times bestselling and Edgar Award-nominated author Deanna Raybourn. Billie, Mary Alice, Helen, and Natalie have worked for the Museum, an elite network of assassins, for forty years when they are targeted by one of their own. Now to get out alive they have to turn against their own organization. They're about to teach the Board what it really means to be a woman - and a killer - of a certain age.