V.I. Warshawki, our favorite Private Investigator is back. The hard working, feisty, mouthy, stubborn, sometimes reckless PI has a job to do for her best friend in Chicago, Dr. Lotty Herschel. There is is no hesitation. V.I. is is ready. Vi must track down the daughter of a friend from Vienna in World War II. Lolly and her childhood playmate escaped the Holocaust and though they have drifted apart, Lolly must help her daughter, Judy Binder, who is troubled and a serious drug addict.

If you enjoy a mystery about science, history, spies, multi-generational dysfunction filled with too many family secrets and lies, you will love CRITICAL MASS. The action goes back and forth from present day Chicago to Vienna in the past around the 1930's. The complicated plot will keep you guessing until the end when our favorite private eye finds the truth she has been seeking and a smashing surprise.

This plot is filled with action but complex plots and subplots. Ground breaking research done by women scientists and physicists in Germany in the war, the race for the atomic bomb ,the beginnings of the computer age, the rise of Homeland Security in our country, drug culture in Chicago, and an insight into women and misogyny in the field of Science in the years before and after World War II. Secrets go back to Germany, Austria, Japan and England. Complex characters are weaved into a plot that is surprising, scary but keeps your attention.

Vi's neighbor and protector, Mr. Contreras, adds some fun to this dark plot. He cooks for his "doll", takes care of her dogs and is always there to listen. A little romance with Jake, the bass player, via telephone and later in Vienna where Jack tells Vi, "I can play a dirge if someone drops your body into the Danube."

It's thrills, chills, and social ills in this high- tension drama that will keep you riveted. CRITICAL MASS is another dazzling achievement from Sara Paretsky, that I found hard to put down.