Wealthy Richard Abernethie dies unexpectedly, and his several surviving relatives, who hardly keep in contact with each other, gather for the funeral. His much younger sister, the ditzy and dreamy Cora Lansquenet, blurts out that he was murdered by someone of the family, to everybody's apparent shock. Cora is immediately apologetic and says she was mistaken, so the discussion doesn't go any further, but just one day later, Cora herself is found brutally murdered
The novel provides examples of:
- Awful Wedded Life: By all accounts, Pierre Lansquenet was a terrible husband to Cora. She adored him nevertheless and never forgave her family for their treatment of him.
- Babies Make Everything Better: The reveal of Rosamund's pregnancy improves her family life a lot.
- Giftedly Bad: Everybody except Cora sees Pierre's paintings are terrible.
- I Never Said It Was Poison: The reason why the German translation is titled The Wax Flower Bouquet for a decoration mentioned in passing at most. Miss Gilchrist says the wax flowers look nice on the malachite table, except that she couldn't have seen them they were only there on the day of the funeral, when Miss Gilchrist was at Enderby masquerading as Cora Lansquenet.
- In the Blood: There is a definite streak among the Abernethie women to fall deeply in love with undeserving husbands who don't love them back half as much.
- Inheritance Murder: Richard is believed to be murdered by someone impatient to get the inheritance. Cora's death is quickly figured out to be a She Knows Too Much murder precisely because she hardly leaves any inheritance to speak of a few hundred pounds to Susan and several sketches and a brooch to Miss Gilchrist. While in fact, Cora's murder is committed for the inheritance among her possessions there is a Vermeer, over which Miss Gilchrist paints a sketch to resemble one of Cora's.
- Insufferable Genius: What Cora believed her husband to be. Everyone else knows he was insufferable but definitely no genius.
- Never One Murder: Richard Abernethie and Cora Lansquenet, and attempted murders of Miss Gilchrist and Helen Abernethie. Subverted: only Cora's murder and the attack on Helen are real. Richard died a natural death and Miss Gilchrist staged and exaggerated her own poisoning.
- Not So Different: Rosamund Shane is very similar in character to her aunt Cora Lansquenet, though in appearance the two couldn't have been less similar.
- Obfuscating Stupidity: Miss Gilchrist claims to have no understanding of art and painting, so that nobody would think they are, in fact, able to recognize a Vermeer immediately and later perfectly imitate Cora's style when painting a sketch over the Vermeer to conceal it.
- Old Retainer: Lanscombe, the faithful butler of the Abernethies, is close on ninety and extremely devoted to the family he has served for many decades. Richard recognizes it as he leaves him an annuity.
- Parenting the Husband: The reason why Maude Abernethie encourages her husband's hypochondria. She has a strong motherly instinct but no child of her own, so she projects all she has onto Timothy.
- Sanity Slippage: The murderer slips into happy ravings after getting arrested, and it is discussed that they might end up in Broadmoor.
- Supreme Chef: Miss Gilchrist is an amazing baker. Before the war, she used to have a tea-shop of her own.