One of the main characters is a graduate student pursing a Ph.D. in biostatistics, who notes to police detectives that coincidences in the circumstances of several murders are statistically significant, i.e. the probability that they are unrelated is very small indeed. The key deduction that the murders were carried out by one individual leads the student and the police to focus on figuring out the characteristics of the killer -- "what do these victims have in common and who would have the motive to kill all of them?" -- and eventually allows them to locate and stop the criminal.

The mathematical content of the book is pretty sparse. However, the one statistical deduction is central to the plot, and the life and mind of the ever-present graduate student adds a nice touch and is central to the atmosphere of the book, which is sort of in the airport thriller/mystery genre rather than having great literary pretentions (as far as I am concerned). Nonetheless, a fun read.