This is one Agatha Christie that I had not read, for some unknown reason, for some time. I had even forgotten whodunnit, which is unusual. A lot of times that's ALL I remember. This one surprised me. There's some real darkness at its core that's very different for a Poirot novel. There's a lot about politics (mostly radical), innocent people being harmed, and a very cold-blooded psychopathic killer just full of excuses for their behavior. I really loathed this killer for their flippant disregard of other people's lives.

“Yes, we are all human beings. That is what you have not remembered." (Hercule Poirot)

The story starts simply - and humorously - enough with Poirot going to his dentist, Dr Henry Morley. Later, Poirot learns that Dr Morley is dead - supposedly a suicide. When another of Morley's patients, Mr Amberiotis, dies of an overdose from a dental anesthetic. Did Morley commit suicide when he realized what he had done? Of course, it's not that simple - it never is with Christie. Then another patient of Morley's, Mabelle Sainsbury Seale, vanishes.

To say anything else would ruin the fun of reading this excellent Agatha Christie. Very recommended.