Whilst it's not particularly unusual to have a flawed central protagonist, unapologetic ones are less common. Add being female, and that makes IN HER BLOOD's Catherine Berlin a rather rare beast, and a very welcome one.
Set in London after the Global Financial meltdown, Berlin is a government investigator who receives a tip-off about a local loan shark, then finds her informant floating in the Limehouse Basin, brutally killed. The first complication is that her female informant has been anonymous, and even the police seem to have trouble identifying her. The second complication is at the same time a notorious doctor is murdered and the pharmaceutical heroin he provided on prescription to registered addicts stolen. Leaving Berlin with the third complication of only finding a very limited temporary source, and the final, really big complication of sorting out a permanent alternative supply.
Berlin is a registered heroin addict, completely opposed to more mainstream treatment options, including methadone, she's an addict who had some measure of control over her addiction... as long as her doctor was alive.
Hence the flawed, unapologetic protagonist. Berlin (she doesn't use Catherine) is completely aware of her addiction and firmly of the opinion that she has it under control. Which makes the sudden inaccessibility of the ongoing medical supply a rather interesting problem for her. Hauxwell has pulled off a balancing act - on one hand you can see that it's not going to take much of a push for Berlin's life to spiral out of control, and at the same time you can see she's not going to let that push happen without one hell of a fight.
Illustrating the limited supply of heroin, the story is divided into "The First Day", "The Second Day" and so on covering the 5 days of supply that Berlin has. Before it runs out, she has to do something about her own life, and whilst she's aware of that, and thinking of her options, her desire to know who her informant was and solve the murders is also pressing - not least because some of her investigative choices are very compromised by the overriding addiction. These suspect choices provide a very interesting insight into the all-consuming nature of addiction, no matter how much somebody thinks they have it under control. There is quite a bit of that teetering on the edge going on for all the characters - Berlin, her bosses and workmates, the cops, the crooks. Really just about the entire cast have choices to make be they conscious or unconscious.
Early on there was some confusion about the involvement of an independent investigator right in the heart of a series of murder enquiries, but the writing was so sharp, and the way that the plot wove the world of drug addiction and rehabilitation, cops and crooks, high-finance and loan-sharking together was clever and very realistic. But really, the best aspects of IN HER BLOOD was Catherine Berlin who is a surprisingly sympathetic, unapologetic, flawed protagonist.