Christie, Marsh, and Thallium

Researching murder by
poison.

As a follow up to yesterday's post about Agatha Christie's The Pale Horse, I did a little research into the poison used - Thallium. Turns out that element 81 on the periodic table of elements is one of the deadliest. According to Deborah Blum in The Poisoner's Handbook, thallium is colorless, tasteless, odorless and very soluble in a variety of liquids. Would you care for some thallium laced hot chocolate? Arsenic always had to be added to something bitter tasting to help hide the flavor.

In the 1930s, thallium could be found in many pesticides including rat poisons that were easily purchased on the open market. Turns out thallium is also an effective depilatory and was used in cosmetic preparations that would help that discerning lady remove the unwanted hair on her arms or upper lip. Unfortunately, some consumers lost more hair then they bargained for when scalps were made bald, vision was lost, or mobility was impaired. For investigators of criminal activity the classic symptom of hair loss was a key clue.

Ngaio Marsh used thallium poisoning in her novel Final Curtain. (Spoiler Alert) A preparation of thallium was used to treat a group of young children with ringworm, a common occurrence in the day before too many children were sicken or died from the treatment. The murder help him/herself to the medicine to do in the victims of this mystery.

Christie (Spoiler Alert) has the poisoner in The Pale Horse lacing personal care products or packaged foods with thallium. Here too the amateur detective, Mark Easterbrook, figures out what's going on when Ariadne Oliver points out that many of the victims have had their hair fall out. Easterbrook remembers reading about a poisoning case in the States, and finally puts two and two together. In both stories once the source of the poison is figured out the capture of the culprit isn't too far off.

As a high school teacher (I don't watch much TV but I hear this guy from Breaking Bad is giving us a bad reputation), I'm a bit of a science geek and have to admit that all three titles pictured above come from my book shelves. It's amazing what you can learn from a book. Who needs to do a Google search when you have access to great resources. Okay call me old fashioned.