Dr Andersen

In the short story The Flock of Geryon, Dr Andersen is a scientist who ran a religious sect known as "The Flock of the Shepherd" with a commune named "Green Hills Sanctuary" in Devon. He was quite attractive and charismatic and had succeeded in enticing many lonely but wealthy women to join his movement. Some of them made wills leaving their property to the sect and then died later, apparently of natural causes.

Dr Andersen was a chemist by background. He had been expelled from a German university (he claimed because his mother was Jewish but this was later found to be false). He was keen on the study of Oriental Myths and Religions and spent his spare time researching the topic and writing related articles.

Investigations by Poirot and Chief Inspector Japp revealed that Andersen was an exponent of scientific murder. Under a different name, he had set up chemical laboratory in Sheffield in which he prepared various bacteria cultures. When his devotees were gathered for their periodic ceremonies at his retreat, he would inject them with hashish to create episodes of extreme ecstasy. Many of them, especially the lonely women, would, out of gratitude, make wills leaving their money to the cult. Then Andersen would inject them with bacteria cultures grown in his laboratory. These would bring a range of natural diseases at a later time, causing the victims to die, usually at their own homes in various parts of the country, deflecting suspicion from him.