The book opens with a judge in a murder case that Lord Peter Wimsey is attending giving a dry and rather long-winded summary (exposition, rather) of the case in his charge to the jury. A mystery writer named Harriet Vane had shacked up with a Philip Boyes (something that was rather scandalous in 1927) after he told her he was against the institution of marriage. A year later he proposed to her; she said no, on the grounds that she was dishonored—he was just trying her out, as obviously had nothing against the institution of marriage. Boyes could not get over her, and tried to change her mind during several visits over the course of several months. During these months Miss Vane purchased several packets of arsenic, as research for her arsenic-poisoning murder mystery in just how easy it was to procure arsenic. The judge, espousing impartiality, continues to give what seem to be rather leading comments. His last night, Boyes had dinner with his cousin Norman Urquhart, where everything they ate was shared by at least Vaughn, a new (sealed) bottle of Sherry was opened, Boyes himself cooked the final omelette. After dinner he visited Vane, who was unpersuaded, but did serve him a courtesy coffee. Boyes took a taxi back to his cousin’s house, and during the ride he began to have his fatal attack of gastritis, of which he was prone, and had suffered several times earlier that year. After several hours of heated debate, the jury announced that they had irreconcilable differences, in part due to Lord Wimsey’s “eyes and ears,” the chatty spinster Miss Climpson.

Despite the seeming clarity that Miss Vane murdered Boyes with arsenic in the coffee, Lord Wimsey felt that the case was tight, but wrong. He also was much taken with the accused, noting that she was a very intelligent woman (although not, as the narration describes, tending towards beauty). He visits Miss Vane in prison, declares that he will see justice done by working to prove her innocence, and asks if she would marry him. She notes that he is the latest in rather long line of proposals she has recently acquired. He also informs Miss Vane’s lawyers that he will provide them the proof they need; they are somewhat cool to the idea.

Part of the problem with the case against Miss Vane is that she had no reason to murder him, despite the strong (negative) feelings she had towards Boyes. The other part of the problem is that there was not any evidence of anyone else doing it, nor any motive for them to do so. There was no evidence for suicide either, and no amount of searching produced credible evidence for it. Boyes’ last dinner was unusually well-attested that multiple people partook of each element, and Urquhart even the the foresight to preserve the sherry unused since the dinner.

Wimsey paid a visit to Urquhart, who was an estate lawyer. Boyes was related to a very wealthy actress—a rather scandalous career, promoted by the scandalous means a beautiful woman could use. She did use them, and her family had disowned her for her career. In retaliation, she never talked to them, and explicitly said that Boyes would not receive anything because of that. She was now senile, although fairly healthy overall. Urquhart was the executor of the will. In the style of Sherlock Holmes, Wimsey noted that the will had been typed with a typewriter in which one of the letters was chipped.

Wimsey sent Miss Climpson to investigate the actress, and see if she could gain access to the will and take notes on it, as Wimsey thought it was odd that Urquhart had a copy of the will at hand and was so willing to show it to him. Urquhart was in need of a typist, so Wimsey also had Miss Climpson send over one off the staff girls to interview with him. (Wimsey had expanded Miss Climpson’s operation, so that it now included a number of women who did typewriting work; it had the casual look of a typewriting agency, and occasionally one of these women would even be contracted out.)

Miss Climpson made the acquaintance of the actress’ caretaker (after drinking a lot of coffee at coffeeshops waiting for her) by means of the “I think someone dropped this” ruse. The caretaker was chatty, and also into seances. She felt that Miss Climpson was a strong medium, so despite her strong Catholic convictions, Miss Climpson arranged a seance that night. She had been well informed about the techniques used to fake a spiritual manifestation, and she put those techniques to use herself. The second night, the spirit of the actress “visited” and said that she wanted the copy of the will to be taken to Urquhart. A long search ensued, but the will was eventually found in the safe. Miss Climpson used her skills in unsealing envelopes to read the will, in which the actress forgave her family, and left her (substantial) money to Urquhart and Boyes (the remaining relatives).

In the meantime, Wimsey had discovered that Urquhart had invested fairly heavily in a some sketchy stocks.

The typist had been hired by Urquhart. The will arrived, and was received by Urquhart in the presence of two witnesses, which would make it difficult for him to not produce the will when the re-trial arrived. The typist happened to notice a hidden safe in Urquhart’s office one day, when it was not completely closed. She burgled it, and found some packets. She took samples, and Wimsey’s butler, Bunter, who was a bit of a chemist, verified the substance as arsenic. Even Chief-Inspector Parker, who had been convinced of Miss Vane’s guilt, had now come around to Wimsey’s thinking. So Urquhart had poisoned Boyes somehow, but there was no opportunity.

Wimsey visits Miss Vane again, giving her the news, and entreating her to marry him. She refuses again, on the grounds that she is scared to marry, although she would be willing to live with him. Lord Wimsey, however, was not interested in sketchy arrangements, and since they could not come to an agreement, he promised not to bother her about it again. (On the subject of marriage, though, earlier Wimsey pushed Inspector Parker to propose to Wimsey’s sister, whom he had been courting but had been reticent to propose to; she accepts.)

While looking over other arsenic case, Wimsey had an epiphany. He convinced Urquhart’s hair stylist (who Wimsey also patronized, as luck would have it) to save a little bit of Urquhart’s hair and fingernails. Then, he invited Urquhart over, and gave the big reveal: Urquhart put arsenic in a cracked egg that was used for the omelette. He had been ingesting arsenic himself regularly, becoming immune to it in the fashion of certain tribal peoples. He had also drunk nothing during the meal, for he knew that the body will get rid of arsenic if it is used to it, but if it is mixed with water, the body is not capable of ridding itself. Urquhart excused himself to the bathroom and attempted to flee, but Inspector Parker was there and arrested him.

Miss Vane was acquitted following the Crown withdrawing its case against her. She wanted to thank Wimsey, but he driven off immediately after the trial; she found herself disappointed. Her friend observed that she would have to call him (which she refused to do), as he was a gentleman and would keep his word. Wimsey, for his part, expressed to his brother his rather scandalous plan to marry the (formerly) accused, if she would have him.

Strong Poison follows the trend of Sayers; mysteries, where the mystery is not so much on who did it but how. Urquhart falls under suspicion early on, and events rather quickly suggest that he did it. As the book unfolds, we are informed of how he did it. However, the mystery is not the strongest feature of the book, but rather the question of will Lord Wimsey be able to prove the innocence of the girl he has become quite besotted with. This is, in fact, quite unusual. Wimsey has hithertofore take little notice of women, especially after his detective hobby turned into a full-time (but private) job. He has been quite cool in every situation, yet is suddenly taken by this girl who is accused.

People have commented on Vane and Wimsey, and it is hard to escape the thought that Miss Vane is a bit of a personal fantasy of Sayers. Like Sayers, she was a mystery writer. Like Sayers, she is an intelligent woman, in an society where intelligence was not the desired feature of women. Like Sayers, as the introduction written by one of Sayers colleagues says, Miss Vane did not incline towards the beautiful. In fact, Sayers herself had a lover who expressed disdain for monogamy, but then later married. Lord Wimsey was nobility, but also someone who appreciated all the things Sayers was. What woman would not want to have a man completely taken by all the things she herself values? It should be noted that at the time of writing Sayers had been happily married for four years, but nonetheless, it is still hard to escape the idea of Miss Vane being Sayer’s personal fantasy.

The book also has a very ends-justify-the-means ethic. In addition to my personal strong disagreement with this ethic, it seems a poor choice for someone interested in justice. Is burglary—speculative burglary, in fact—justified in the service of justice? Is acting against your own morals, as Miss Climpson does as a medium, the path to justice? Bunter even prosecutes a romance with one of Urquhart’s servants, but then, presumably, disappears. Bunter was acting under direction from Wimsey, but there is a limit somewhere. In point of fact, either Wimsey or Bunter uses romance just the way that Miss Vane accuses Boyes of treating her.

The love story is unrealistic, and unsatisfying. No good reason is given for Wimsey falling in love with her; something more than intelligence observed in the courtroom would be necessary for a nobleman (even minor nobility) to proposed to an accused murderer. In fact, not even a member of the ordinary class would likely take that risk, nor would such a man propose to a girl he’s never spent time with. For a member of the nobility to do both may be a pleasant fantasy for Sayers, but it is not believable. Furthermore, while there are good reasons to reject a proposal such as Wimsey’s (largely the corollaries to the reason he should not have given the proposal), she does not use any of them, choosing the weak way out with a vague “I’m afraid of marriage.”

This is not Sayer’s strongest work. The plot tension comes almost entirely from the shortening timeline to prove Harriet Vane’s innocence. The mystery is definitely a “mystery” in the sense of literal definition of “something revealed,” as the reader does not actually have the information necessary to solve the mystery until it is revealed. This is more of a novel that uses mystery and murder, rather than a murder mystery. The plot is linear and the characters have little development. The ethics are questionable. If the purpose was to show Wimsey’s desperation, then Sayers succeeds brilliantly, because the novel feels like a desperate rush.