Kerr leaps from postwar Germany (A German Requiem, 1991, etc.) to London in 2013 to tell a challenging story of freelance social engineering. Fear of epidemic serial killings has prompted the creation of the Lombroso Institute, which has isolated VMN, a neurological inhibitor of male aggression, and compiled an exhaustive list of men deficient in that substance. One man, shocked that he has tested VMN-negative, breaks into Lombroso's database, retrieves the names of other negatives, and uses them as a hit-list, killing men who fit the neurological profile of potential serial killers. Before he erased his own files, the killer was code-named Ludwig Wittgenstein, and as Wittgenstein he conducts an intricate dialogue with Inspector Isadora (Jake) Jakowicz--the man-hating officer who's put another serial-killing investigation on the back burner in order to nail him- -comparing detective work to philosophical inquiry and raising questions about knowledge, proof, and reality in unnervingly dramatic contexts. Kerr doesn't stint on either the technical or the philosophical side of his futuristic landscape: the result is the bleakest, brainiest thriller to come along in years.