Killers of a Certain AgeBy: Deanna Raybourn Older women often feel invisible, but sometimes that's their secret weapon. Billie, Mary Alice, Helen and Natalie have worked for the Museum, an elite network of assassins, for forty years. But now their talents are considered old school and no one appreciates their real world resourcefulness in an age of technology. When the foursome is sent on an all expenses paid trip to mark their retirement, they are targeted by one of their