The third Catherine Berlin novel from Annie Hauxwell takes the concept of moving a character out of their comfort zone that bit further. Berlin is one of those unrepentant flawed types. A heroin addict she's prepared to manage the addiction with prescription medications, but she's really not able / or willing to give up totally. Anything that threatens her supply of drugs has a major impact on her comfort zone. She's also a welded-on resident of London. She knows her area very well, often walking miles of a night to soothe the cravings and distract her brain. Taking her to Moscow breaks her final connection with comfort. Not only does she find herself in a city she doesn't know, they speak a language she doesn't and early on the piece, her passport and her medications are taken from her.
From the absolute outset tension builds well - with the distinct sense of something dodgy about the offer of a job in Moscow. Even though the chance is handed to her by her oldest friend (and an ongoing character), everything is odd. Sending a freelance investigator like Berlin seems like a peculiar choice, and whilst it could seem very staged from the start, it works, mostly because just about everything that Berlin gets involved in comes from the dodgy end of the scale.
Whilst the crime and mystery elements in this plot are, as always, strong and nicely complex, the attraction of these books are the characters. Berlin and Charlie, her substitued translator, form an interesting partnership, albeit with the distinct feeling of two people circling each other in the ring. Neither of them is a straight-forward woman, and both of them have secrets they are hiding, and complications they are dealing with. In the earlier books Berlin has played more of a solo hand, and whilst she navigates much of the unknown, and the threats in Moscow herself, frequently she has to work with Charlie, they have to reach some understanding. It's very well done.
It may be that the lurking Russian threat and the questionable conduct of the local police are a bit harder chewing for some readers. In this case it does work, although you are going to have to accept the complicated web of corruption, deceit, illegality, dirty money, gangsters and authorities. It all comes down to the power of the story telling, the pace of the action and the amount of connection a reader can establish with Catherine Berlin. To do that you're going to have to understand why she's so flawed, and accept that this is her comfort zone. Because of that it would probably be preferable if you read the first books in the series before tackling A MORBID HABIT. Which should be no trial whatsoever.