When Myra Harrison, an English visitor to South Africa, was found dead, her body had no disease, there were no marks of violence, and pathological examination gave no reaction to any known poison. Yet, she had been murdered; there was no other explanation. Then two more people died - in England - and, once again, their bodies were found to be perfectly healthy. Scotland Yard were called in, but it was Doctor Manson who eventually found the answer to the mystery.
2.5 stars, really. It's not bad or badly written, just very slow getting started. And the central idea of the book, a particular untraceable poison, is a pretty commonly known poison now (and perhaps now is traceable), so the plot has a lot less tension and interest than it might have had when the book was written.
This entire review has been hidden because of spoilers.