A Drink Before the War is the first in a string of mystery novels by Lehane that feature the same crime-fighting detective pair: Patrick Kenzie and Angela Gennaro.
This first mystery is set in Boston and involves a seemly inept cleaning woman. Early on in the the first story of the series, we get a whole lot of exposition on Kenzie and Gennaro. However, it isn't long before the two private investigators are hired by the senators at the State House to find the cleaning woman who has escaped her job (and their scrutiny) with some of their private documents.
Kenzie and Gennaro soon learn that the cleaning woman, Jenna Angeline, didn't steal any private documents at all. What she has is a son who heads one street gang and a husband who heads the rival street gang. Angeline also has a very angry sibling and a picture condemning one of the politicians (because it shows the politician in a hotel room with her husband). Could THAT be the "document" the politicians keep griping about? My guess is, yes!
I find it interesting that Angeline decides to help the investigators. Angeline quickly vows to help Kenzie with the case. Unfortunately, she is killed almost immediately, beginning a war between the husband vs. son rival street gangs. The two private investigators plan to apprehend those who are truly guilty here & succeed in the midst of their own issues.