This isn't a thriller, despite what the mysterious cover and ominous (and somewhat obvious) title would have you believe. It instead is a slow-moving, methodical account of one elderly woman's struggles with dementia and her attempts to be taken seriously when it turns out that her friend Elizabeth is nowhere to be found. The book proceeds pretty much in real time, with the narrator, Maud, illustrating basically every part of her day and in doing so revealing the sad ways in which dementia changes how you live, and even somewhat who you are. 
 Nobody close to me has suffered from dementia, and I know very little about it. I can't really even remember any other portrayals of it in popular culture, or at least any in which it was the central focus of a story. Hence, I can't speak to how accurate Healey's writing is. However, I can say that it never felt like she was being flippant with her treatment of dementia. Maud comes across as a real human being, and her condition is never used to poke fun or portrayed in any way other than very matter-of-factly. Indeed, it was extremely sad reading Maud's thoughts about how she is perceived and the dismissive, mocking tone with which some talk to her, sometimes including her own daughter. The tendency of people to treat Maud as either someone who does not know anything and cannot think for herself, or someone who may as well be on their deathbed and must be treated with the utmost caution and gentleness, certainly rings true, and seeing the way that people navigate both sides of that spectrum as well as the response Maud has to those sides was very engaging. 
 I guess now is a good time to say that this is a book with two stories in it: one that deals with a woman who is losing her memory and looking for her friend, and one that deals with that woman in her childhood, looking for her sister. The flashbacks are presented with basically no segue, as each break in the main story leads directly in to a vivid recollection of Maud's life as a teenager in postwar England. This second story is notable because it is so normal: it doesn't have the unreliable narrator that you quickly get used to in the rest of the book, and instead tells a fairly straightforward story about her childhood in a very standard way. Indeed, the way that the stories are interleaved is rather jarring, and had the effect of acting as a kind of foothold throughout the novel; even if I was struggling to keep up with the disjointed style and emotional content of the story, I could always count on a flashback coming to ground me and allow me to learn a bit more about Maud herself as well as her family. I did often wonder, however, how Maud was able to have such clear memories of events from her distant past. It may be that this is a realistic portrayal of dementia; I just don't know. As someone who is generally not very interested in history, the descriptions of postwar England just passed right by without any kind of impact. However, it was engaging enough when taken as short intervals between episodes primarily due to the mystery angle. 
 As I said above, more than anything, this is a very slow book. Healey chooses to focus a great deal on Maud's day-to-day, which when combined with the sometimes circular path of Maud's memories and thoughts, results in a book where nothing much happens for a long time. Thus, this book worked better for me as a vehicle for exposing me to a disorder and perspective on life that I really had no knowledge of, than as a gripping read. 
 Healey does her best to make Maud a real, round character despite her difficulties, and while she succeeds for the most part, there are parts where the characterization takes a back seat to the central conceit of depicting someone with dementia as faithfully as possible. This resulted in somewhat of a not-quite-full experience when I was done. In fact, quite a few parts of the story contributed to that feeling. The ending is convenient and somewhat predictable, and really had no bearing on how much I enjoyed the book. Many parts of the plot were simply an excuse to spend more time in Maud's head or past, and it would've been nice to be able to think about the plot and engage with it as much as I engaged with the narration. Hence, I'm not sure I'd really recommend this book; I certainly don't regret reading it, and feel like it will be a fairly singular experience, but its faults are also fairly obvious. However, as I already mentioned, I did feel it was worthwhile, and I really flew through the last quarter or so. I'm excited to read more of Healey's works in the future, as I appreciated her ability to make this book so engaging and emotional without relying on plot twists or getting overly sentimental.