In this 16th book featuring the spunky, fierce and loyal private detective V.I. Warshawski, an ominous phone call sets a chain of events into motion that trace all the way back to Vienna during World War II. As a favor to her friend, Dr. Lotty Herschel, V.I. takes on a mysterious but seemingly routine missing person case. Judy Binder, the daughter of one of Lotty’s childhood playmates, has disappeared. 

V.I.’s first lead takes her to a small farm town outside of Chicago that turns out to be a meth house. She finds one dog dead, another near death, and the body of a man in the cornfield who was obviously murdered. Although she doesn’t find Judy, the corpse turns out to be connected to the missing woman. 

"Sara Paretsky mystery capers are always full of twists and turns, including surprising elements that this reviewer eagerly anticipates when reading her books. CRITICAL MASS is a complex family mystery that reaches from the past into the modern day, and is one of Paretsky’s best."

Next, the investigation takes V.I. to Skokie, where she interviews Kitty Saginor Binder, the missing woman’s mother and Lotty’s old friend. Kitty and Lotty share a tragic past, as survivors who escaped the Holocaust on the Kindertransport from Vienna to London in 1939. Kitty tells V.I. that her father is a Nobel Prize-winning scientist and that her mother was a scientist in her own right. As Kitty shares the heartbreaking story of her early life, V.I. begins to understand more about her family and her daughter. She also discovers that Judy’s son Martin has also gone missing. No one has heard from him in over a week. V.I. begins to wonder if the disappearances are connected.

To find out, V.I. visits Metargon, the high-tech company where Martin works as a computer engineer. Metargon executives are looking for Martin too, concerned that sensitive industry secrets might have been compromised. The company is more than a little suspicious of Martin’s disappearance.

When V.I. digs deeper into Metargon’s corporate background, she learns that the current head of the company is connected to Kitty’s past. A multi-generational mystery that dates back to the 1930s and the race for the atomic bomb starts to take shape. Soon the disappearances of Judy and Martin take on new meaning as layers of politics and corporate greed are revealed. V.I. finds herself entangled in a treacherous web of secrecy that involves national security, drug lords, corrupt government officials, wartime family secrets, intellectual property and patent law. The closer V.I. gets to the heart of it all, the more she endangers herself. But she never gives up.

Sara Paretsky mystery capers are always full of twists and turns, including surprising elements that this reviewer eagerly anticipates when reading her books. CRITICAL MASS is a complex family mystery that reaches from the past into the modern day, and is one of Paretsky’s best. Underscoring the riveting suspense is the heart-rending horror of WWII and the Holocaust, complicated even further by political and scientific power-brokering. It takes a character like V.I. Warshawski, who is willing to see justice served at any cost, to get to the truth. And this is exactly what has endeared Paretsky’s time-tested heroine to so many faithful readers --- especially this reviewer.