This is fun - a locked room mystery, except instead of a room someone's been murdered in a car in the middle of a traffic jam, and it seems that no one could possibly have done it without being seen. Fortunately, also stuck in this traffic jam is off-duty police officer Belinda Kidd, and she has to sort through all the bystanders and their multiple problems to get to the solution of who killed this apparently random victim.

It's a great concept, and it zips along nicely. Kidd is sympathetic - a middle-aged officer on the verge of burnout, ready to retire and navigating trauma and menopause - and I felt for her. I think this is a one-off, but if it turned into a series I'd read them, primarily because of the protagonist. I do think that Furniss might have gone a little overboard piling miserable life experiences onto her, but the story mostly avoids being overwrought there so I'm inclined to gloss over that particular issue.