Not bad for one of Margaret Millar's earliest published works. I thought the mystery progressed pretty well. The pacing is good, and we are given clues at a constant rate. I never guessed Jane was the murderer, even after the revelation by the handwriting expert that the letter warning of the murder was probably written by a woman. Dinah makes a much more likely suspect because she seems so determined to make herself unliked. I wish I could have read the first two Paul Prye mysteries to get some experience with his character, but this was the only one the library had. The inspector seems awfully quick to let Prye into his confidence, and even have him do some of the detective work, after being overly suspicious when they first meet.
Most of Prye's explanation of how and why Jane commits the murders makes sense, but I have a few little problems with it. It's hard to believe that Jane would even think to poison herself first to deflect suspicion, and she manages to pick a method that doesn't inflict any lasting effects. Her using parts of Duncan's letter to her in the warning letter to Prye doesn't seem to serve a purpose. It only works if Duncan's death is ruled an accident; only then can it be believed that Duncan really tried to murder his sister, and the call to the hospital to say what kind of poison she was given rules out Duncan as the poisoner. Jane's attempt to show that someone else stole the letter and copied parts from it meets with the same problems. Next is Duncan's murder. No one could know what time Duncan would wander home. If he had come home earlier while the rest of the household was still awake, or the next morning, Jane would miss her opportunity to kill him. Unless he has a habit of getting drunk in the afternoon and coming home at midnight, Jane gets awfully lucky. Jackson says the door is the kind that locks itself automatically, so no one can open it from the outside without a key. However, Duncan finds it actually unlcked, so Jane must have left it ajar or jammed something into the bolt, and she would have to be sitting in the hall waiting for him. Finally, I find it surprising, although possible, that Jane thinks to cover her tracks with Sammy Twist. On the other hand, it was pretty stupid to lure him to the house where someone could have seen one of them, or gone into the bathroom and found the sheets tied to the toilet (incidentally, would the toilet be strong enough and firmly attached enough to support her weight?). She also tells him to knock on the back door, so she has to make sure to knock him out before he knocks, or the policeman stationed in the house would probably hear. She also must be awfully strong to get hom from the back door to the garage, however far that is, and actually lift him up into the rumble seat of Prye's car. So, Jane as murderer: I'll buy it, but I don't really like it.
There is a certain lack of emotion, despite all the angry words. Prye and Nora were getting married, and aside from him kissing her twice in the whole novel, we hardly see that they care about eachother at all, and they hardly even speak to eachother. Nora gets very little dialogue period, and is probably the most boring character in the family. I also don't know how Nora feels about any of her cousins, besides getting pretty tired of listening to them after a couple days, as anyone would. She invites Dinah and Jane to be her bridesmaids, so she must like them somewhat, unless it was the custom to use relatives instead of friends in those days. Mrs. Shane doesn't seem to moved by any of the events, except to constantly go back to the wedding gifts. Worrying about manners and propriety must be her coping mechanism. I also found it odd than Inspector Sands keeps asking Nora questions about the was the household is run, which I would think he would ask her mother, such as about the servants, and the heating of the basement. I thought for sure the money was hidden in the air conditioning unit that is no longer used, since I see no other reason for it to be dragged into the story. I admit I don't know why Dennis started a fire in the fireplace after, presumably, discovering the money hidden behind it. I don't know why that would make him think that would make someone else less likely to find it there. The other alternative is that Jane started the fire for the same reason, but Prye doesn't allow for that in his timeline of her actions.
Overall I enjoyed the read, and I know from reading a few of Millar's later novels that her writing improves across the board, and she is definitely worth reading. An Air That Kills is my favorite so far.