Jill Johnson on The Dose Makes The Poison

Crime writers love poison. It’s the murder weapon of choice for a woman. It doesn’t require physical strength and it’s easy to administer to an unsuspecting victim. Also, it can take hours, sometimes days to take affect during which time the murderer can flit away to some safe place - perhaps on the other side of the planet - before the detective has even assigned a crime number. 

Crime writers love poison but as Paracelsus said five hundred or so years ago,

‘All things are poison, and nothing is without poison; the dosage alone makes it so a thing is not a poison.’

Or, to use the shorter, more familiar version ‘the dose makes the poison,’ meaning that anything and everything can kill if the dose is right - even water and oxygen. 

Paracelsus was a Swiss physician, alchemist, astrologer, theologian and philosopher, an all-round Renaissance man. He lived in the late 14 and early 15 hundreds and died at the ripe old age of 47. Not bad for the times. He is credited with being the ‘father of toxicology’ but like all respectable Renaissance polymaths, he believed everything was connected. The study and use of poisons was just one of the many tools in his medical box.

Crime writers love poison and it’s their job to get the dose right, which can be tricky when anything and everything can kill… but if their protagonist is a professor of botanical toxicology, then at least someone knows what they’re doing.

The protagonist in Devil’s Breath is Eustacia Amelia Rose, professor of botanical toxicology at University College London. She would most certainly have studied Paracelsus when she was a student. Like him, she would also have undertaken many research projects focusing on harmless, dangerous and fatal doses of poison. She would definitely know the most effective way of introducing a toxin into a body. In fact, her vast knowledge would make her an unparalleled expert in plant poison murder. Which is why, when someone dies after being injected with a fatal dose of a toxin extracted from a rare and extremely poisonous plant, she becomes DCI Roberts’ prime suspect. 

The interesting thing about the toxins from poisonous plants is that although a large dose can kill, a small dose can actually cure. Take the yew tree, the most poisonous tree in the U.K. It produces a poison called taxine which can kill in 20 minutes. But it also produces a medicine called taxol which is used for the treatment of breast cancer.

Meadowsweet and the willow tree contain salicylic acid, natures version of Asprin. A small dose can help with pain relief. A large dose will thin your blood and cause internal bleeding.

If Vinca major, common name Periwinkle, is ingested, it can dramatically lower your blood pressure and cause heart arrhythmia. It also stops the production of white blood cells, which can kill you. But it also produces a medicine that can save the life of people with leukaemia… the dose makes the poison.

Crime writers love poison. Agatha Christie wrote 85 books. 41 of them, almost half, included poisons and about a quarter of those were plant poisons. Hyoscyamine from Henbane, nicotine from Nicotiana, ricin from the Castor Oil Plant, asprin from Willow Trees, aconite from Monkshood, morphine from Poppies, taxine from Yew, belladonna from Deadly Nightshade and gelsemium from Yellow Jasmine feature in books such as A pocket Full of Rye, And Then There Were None, Dead Man’s Folly and They Do It With Mirrors. She drew much of her inspiration from her garden at Greenway, her house in Torquay and it’s widely acknowledged that although most of her poisons knowledge came from her years working in a pharmacy, her prolific use of plant-based chemicals in so many of her books is a testament to her gardening expertise.

Crime writers love poison. I’m no exception. The title of my crime mystery Devil’s Breath comes from the street name for the powdered seeds of the Columbian Borrachero shrub. The compound, which contains the chemical scopolamine, has been used in South American spiritual rituals for hundreds of years and is said to cause hallucinations, frightening images and a lack of free will. It was the lack of free will that I was most interested in. In the story, the protagonist Professor Rose becomes infatuated with a beautiful Brazilian woman. Pursuing her leads the professor into situations she would never ordinarily enter and encounters with people she would never ordinarily meet. The Brazilian has a hold over the Professor. As powerful as if the woman had blown Devil’s Breath powder into her face.

Devil's Breath by Jill Johnson (Bonnier Publishers) Out Now

I've always been better with plants than people . . . Eustacia Rose is a Professor of Botanical Toxicology who lives alone in London with only her extensive collection of poisonous plants for company. She tends to her garden with meticulous care. Her life is quiet. Her schedule never changes. Until the day she hears a scream and the temptation to investigate proves irresistible. Through her telescope, Professor Rose is drawn into the life of an extraordinarily beautiful neighbour, Simone, and nicknames the men who visit her after poisonous plants according to the toxic effect they have on Simone. But who are these four men? And why does Eustacia Rose recognise one of them? Just as she preserves her secret garden, she feels inexplicably compelled to protect her neighbour, but Eustacia soon finds herself entangled in a far more complicated web than she could ever have imagined. When her precious garden is vandalised and someone close to Simone is murdered with a toxin derived from a rare poisonous plant, Eustacia becomes implicated in the crime.  After all, no one knows toxic plants like she does . . .