After more than a year of laying low, Billie, Helen, Mary Alice, and Natalie are called back into action. They have enjoyed their time off, but the lack of excitement is starting to chafe: a professional killer can only take so many watercolour classes and yoga sessions without itching to strangle someone... literally. When they receive a summons from the head of the elite assassin organization known as the Museum, they are ready tackle the greatest challenge of their careers. Someone on the inside has compiled a list of important kills committed by Museum agents, connected to a single, shadowy figure, an Eastern European gangster with an iron fist, some serious criminal ambition, and a tendency to kill first and ask questions later. This new nemesis is murdering agents who got in the way of their power-hungry plans and the aging quartet of killers is next. Together the foursome embark on a wild ride across the globe on the double mission of rooting out the Museum´s mole and hunting down the gangster who seems to know their next move before they make it. Their enemy is unlike any they´ve faced before, and it will take all their killer experience to get out of this mission alive.