The Science of Mysteries: An Overdose of Strychnine


From cover of The Mysterious Affair at Styles, Agatha Christie, 1920

by Deborah Blum

There is altogether too much strychnine about this case
The Mysterious Affair at Styles, Agatha Christie, 1920.

In the midst of World War I – or so the story goes – a young Englishwoman received a literary challenge from her sister. Could she write a mystery novel in which the true villain was impossible to guess?

The response to that challenge was a tale of strychnine and murder that launched one of the most successful careers in crime fiction. No exaggeration whatsoever: the book was published, after several years of publisher hunting, in 1920; its title is The Mysterious Affair at Styles; its brilliant fictional detective is called Hercule Poirot and its author (30 years old at time of publication) is named Agatha Christie.

Christie would go on to write about 65 detective novels and some 14 short story collections (not to mention the occasional play) before her death in 1976. Over the years, sales of her books reportedly have reached close to four billion. But for purposes of this poison-obsessed blog, let us stipulate her dazzling success, her famed fictional characters, and even her famously intricate plotting techniques. Let us focus instead about another celebrated Christie characteristic: she also was obsessed with poisons.

They were her weapon of choice, so much so that a University of Texas pharmacology professor even wrote a book on the subject, titled The Poisonous Pen of Agatha Christie , a survey of the 30 odd poison murders in the mystery novelist’s 66 books. The poisons spanned such a range that the professor felt compelled, as one reviewer noted,  to include a 76-page alphabetical listing of all the toxic compounds – from strychnine to arsenic to thallium to taxine – and all the related chemistry in the Christie ouevre.

I’ve been reading Christie and admiring her devious plotting since I was a teenager given to raiding my mother’s prized collection of murder mysteries.  Her work and others from  the 1920s and 1930s, a era sometimes called the golden age of detective fiction, always fascinated me. The wickedness of the poisons, the cold calculation of the poisoners in the stories, all influenced my own non-fiction book, The Poisoner’s Handbook, which takes a narrative look at forensic toxicology in that same time period. In an earlier Science of Mysteries post, I paid tribute to another brilliant crime novelist of the time, Dorothy L. Sayers and her well-researched study in arsenic, Strong Poison.

But no crime novelist wrote about poison with such knowledge and enthusiasm as Christie, who once said: “Give me a decent bottle of poison and I’ll construct the perfect crime.” In fact, at the time that Christie began work on A Mysterious Affair at Styles, she had been working as a wartime nurse, had been employed in a hospital pharmacy ( then called a dispensary), and had studied for and passed  a test to become a member of the Society of Apothecaries.

So she began her career with a subject she knew well. And the plot of this first novel involves the strychnine poisoning of Emily Inglethorp,  a wealthy and dictatorial elderly woman living at Styles, a classic English country house. The soon-to-be victim is recently remarried to a mysteriously bearded and slightly smarmy younger man. The marriage has thrown into disarray the inheritance plans of her two step-sons who both also live in the house. Residents also include the exotically beautiful wife of the older son and the love interest of the younger, a nurse who happens  to work in a hospital dispensary, and assorted other suspects.

In fact, it’s very much a first novel,  a writer finding her style. Christie would grow into an author with a smooth style,  skilled in elegant misdirection. The Mysterious Affair at Styles has the misdirection without the elegance. It’s cluttered with quarrels, accusations, footprints, spies, cheating husbands, cheating wives and other misunderstandings among the red herrings litter the landscape. But in my particular version of fandom,  all can be forgiven in admiration of the precise (and elegant) chemistry that underlies the story.

The crime comes one summer morning when the household is awakened by “the most alarming sounds” coming from Mrs. Inglethorp’s locked bedroom. When the door is broken down, the woman is found to be suffering from horrible convulsions, one of which “lifted her from the bed, until she appeared to rest upon her head and her heels, with her body arched in a most extraordinary manner.” She dies shortly later and, triggered in part by those terrifying spasms, a criminal investigation is launched.

The story is narrated by a convalescing British soldier, Arthur Hastings, also residing at Styles. He’s an iconic mystery character,  the one who fancies himself a detective but pretty much misses every clue. Hastings, however, does discover an old acquaintance in the village, a former police investigator from Belgium whom he had met while on the continent. He convinces Mrs. Inglethorp’s relatives to hire his friend – Hercule Poirot – as a private investigator.  They establish a Watson-and-Holmes relationship that continues through a numer of Christie books to follow.

The poison in question is quickly identified as strychnine, famous for inducing such horrifying convulsions. Strychnine is a naturally occurring plant poison, a crystalline alkaloid found in the Strychnos family of tropical trees  and climbing shrubs. The best known of these plants is the Strychnos Nux Vomica tree from Indonesia; the hard, disk-like seeds of the tree are sometimes referred to as vomit buttons.

But that mostly refers to the poison’s very bitter taste.  Its primary effect is as a neurotoxin, binding to motor neurons that control muscles and interfering with neurotransmitters that act to moderate and shut down electrical signals. At lethal doses,  result is a constant barrage of signalling that results in sometimes non-stop muscle contractions, creating the kind of convulsions described by Christie in her book.

At the time that Christie was writing, the chemistry and mechanism of strychnine remained something of a mystery too. The alkaloid itself would not be synthesized until 1954, work done by the American biochemist and Nobel Laureate Robert Woodward. But it was a long established poison, a recognized vermin killer in 17th century Europe. And its impact on the nervous system action was known and well-respected. In low doses, it was even prescribed as neuro-stimulant, a kind of chemical pick-me-up for people complaining of flagging energy.

To further confuse the case, then, the story’s victim, Mrs. Inglethorp, has herself just finished taking a strychnine tonic. But she had been taking it for weeks at far too trace a dose to have triggered the convulsions. The police suspect instead that her evening cup of coffee was poisoned. The coffee, of course, was left sitting on a hall table so  that almost anyone in the house could have poisoned it.

And the coffee theory set up another poisonous puzzle. Strychnine is a notably fast-acting poison; in animals, symptoms often arise within 30 minutes, according to the Merck Veterinary Manual. In humans, as soon as 15 minutes after ingestion, according to the U.S. Centers for Disease Control and Prevention (CDC). Yet Mrs. Inglethorp’s death occurred between five and six hours after she apparently drained her cup.

Strychnine itself is a tricky choice for the homicidal killer because its violent action leads so rapidly to suspicion. During the 19th century – a time when poisoners flourished, largely because forensic chemistry was still in its infancy  – a few notable cases occurred. Probably the best known is that of Thomas Neil Cream, who poisoned a series of London prostitutes with strychnine in the 1890s. Before he was hanged, Cream also took credit for the crimes of  Jack the Ripper. A widely publicized earlier case was that of William Palmer, who was executed for the strychnine murder of a friend but suspected of also killing four of his children, all of died of convulsions before their first birthdays.

These are isolated incidents, though. Killers of the day far preferred to use arsenic, antimony and other poisons that tended to mimic natural illness in their effects. Arsenic only fell fully out of favor in the early 20th century, after scientists proved repeatedly that it was readily detectable in a corpse.

In his recent book, Bitter Nemesis: The Intimate History of Strychnine, author John Buckingham suggests that Christie had, however, studied the Palmer trial for inspiration. He points out that the Palmer case included a coffee pot left out in a hallway so that many people could have put poison in it, an inquest at a village in, a doctor already up and dressed in the middle of the night, and a pharmacist who having sold strychnine to Palmer, believing it was to be used to kill a feral dog. All of those elements occur in The Mysterious Affair at Styles – although in Palmer case, Palmer himself was the overdressed doctor in the night and in the Christie telling, the suspected physician turns out to be (spoiler here) a German spy.

But his larger complaint lies with the chemistry-based solution to the mystery itself. Consider this only a partial spoiler because I’m not going to give away the killers in the case.  I am going to tell you how Christie solved the timing of Mrs. Inglethorp’s death. As Hercule Poirot investigates the killing, one of the clues he discovers is an empty box of potassium bromide powders, a compound used as a mild sedative in the early 20th century.

As Poirot discovers, potassium bromide can be used to precipitate strychnine out of a suspended solution. In other words, by mixing it into Mrs. Inglethorp’s tonic, the killer can cause all the strychnine to settle into a lethal layer at the bottom of the bottle. When she takes the last dose, late at night, long after drinking her coffee,  she receives a concentrated amount of this very dangerous poison.

Buckingham complains: “We are expected to believe that medically unqualified conspirators, whose main talent appears to be running around the village wearing false beards (yes, another spoiler) are party to an obscure piece of physical chemistry that only Christie, a qualified dispenser, and at most a handful of her readers would have known.”

He wasn’t the only person to note this weakness. Christie herself didn’t deny it but she pointed out that one of the characters in the book is, after all, works in a dispensary, is studying for the apothecary exam and leaves her notes and books all over the house. Anyone at Styles could thus have – with a little homicidal enterprise – figured out the chemical ways and means in the case.

And you have to admit that it’s a wonderfully geeky solution to a murder mystery. The book received positive reviews from publications ranging from The Pharmaceutical Journal to The New York Times, which said: “Though this may be the first published book of Miss Agatha Christie, she betrays the cunning of an old hand.” But don’t take their word for it, or Buckingham’s, or even mine. As it was published in 1920, The Mysterious Affair at Styles has outlived its US copyright protections. You can find it at Project Gutenberg and elsewhere for free. And that Miss Agatha Christie would probably have considered a crime as well.

Note: I linked to my Sayers and arsenic piece, from the first round of Science of Mysteries, in the post. If you are curious about the rest of that package, Jennifer’s posts can be found here and here. Ann’s is here.  They are brilliant, of course.

Piece originally published at PLOS Blogs

About the Author:

Deborah Blum is a Pulitzer-prize winning science writer and a professor of journalism at the University of Wisconsin.