Sad Cypress
Agatha Christie
 The novel is written in three parts: in the first place an account, largely from the perspective of the subsequent defendant, Elinor Carlisle, of the death of her aunt, Laura Welman, and the subsequent death of the victim, Mary Gerrard; secondly an account of Poirot's investigation; and, thirdly, a sequence in court, again mainly from Elinor's dazed perspective. In the first part, distant cousins Elinor Carlisle and Roddy Welman are happily engaged to be married when they receive an anonymous letter claiming that someone is "sucking up" to their wealthy aunt, Laura Welman, from whom Elinor and Roddy expect to inherit a sizeable fortune. Elinor immediately suspects Mary Gerrard, the lodgekeeper's daughter, to whom their aunt has taken a considerable liking. They go down to visit their aunt: partly to see her and partly to protect their interests. Mrs. Welman is helpless after a stroke and speaks of a desire to die, most notably to Peter Lord, her physician. After a second stroke, she asks Elinor to ask the family solicitor to prepare a will under which it is clear that Mary is to be a beneficiary. Roddy has fallen in love with Mary, provoking Elinor's jealousy. Mrs. Welman dies intestate during the night and her estate goes to Elinor outright as her only surviving blood relative. Subsequently, Elinor releases Roddy from the engagement and makes moves to settle money on him (which he refuses) and three thousand pounds on Mary (which Mary accepts). At an impromptu tea party thrown by Elinor for Mary and Nurse Hopkins, Mary dies of poison that had supposedly been put into a fish-paste sandwich. Elinor (who has been behaving suspiciously) is put on trial. Worse, when the body of her aunt is exhumed it is discovered that both women died of morphine poisoning. Elinor had easy access to morphine from a bottle that apparently went missing from Nurse Hopkins’s bag. In the second part of the novel, Poirot is persuaded to investigate the case by Peter Lord, who is in love with Elinor and wants her to be acquitted at all costs. Poirot's investigation focuses on a small number of elements. Was the poison in the sandwiches, which everyone ate, or something else, such as the tea that was prepared by Nurse Hopkins and drunk by only Mary and herself? What is the secret of Mary Gerrard's birth, which everyone seems so keen to conceal? Is there any significance in the scratch of a thorn on Nurse Hopkins's wrist? Is Peter Lord right to draw Poirot's attention to evidence that someone watching through the window might have poisoned the sandwich, thinking that it would be eaten by Elinor? In the third part of the novel, the case appears to go badly for Elinor, until her Defence unveils three theories that might exonerate her. The first (that Mary committed suicide) is difficult for anyone to really believe, and the second (Peter Lord's theory of the killer outside the window) is unconvincing. But the third theory is Poirot's. A torn pharmaceutical label that the Prosecution supposed to have held morphine hydrochloride, the poison, had in fact held apomorphine hydrochloride, an emetic. This was revealed because on an ampoule, the M in Morphine would be capital; Poirot finds a lowercase M&nbsp;– thus it isn't morphine. The capitalized prefix "Apo" had been carefully torn off. Nurse Hopkins had injected herself with this emetic, apomorphine, in order to vomit the poison that she had ingested in the tea, which explains her quick departure from the table as soon as the tea was consumed that fateful day. Her claim to have scratched herself on a thorn is disproved when it is revealed that the rose tree in question was a thornless variety: Zephyrine drouhin. If the means were simple, the motive is complex. Mary Gerrard is not the daughter of Eliza and Bob Gerrard. Instead—as Poirot has discovered from Nurse Hopkins in the course of the investigation—she is the illegitimate daughter of Laura Welman and Sir Lewis Rycroft, which made her the heiress to Mrs. Welman's estate since she was actually a closer relative than Elinor. When Nurse Hopkins encouraged Mary to write a will, Mary was prompted to name as beneficiary the woman that she supposed to be her aunt, Mary Riley (Eliza Gerrard's sister), in New Zealand. Mary Riley's married name is Mary Draper. Mary Draper is none other than Nurse Hopkins as two witnesses of the defence (Amelia Mary Sedley and Edward John Marshall, both from New Zealand), confirm in court. Poirot ends the novel by rebuking Peter Lord for his clumsy efforts to implicate the hypothetical killer outside the window. He has planted evidence and led Poirot to it in a desperate bid to free Elinor. Lord's momentary embarrassment is presumably alleviated by Poirot's assurance that it is to him, and not to her former love Roddy, that Elinor is now likely to become married.