Note: The play by Agatha Christie has been adapted into novel-form by Charles Osborne.
Hercule Poirot has been called to aid a highly respected scientist working on a top-secret weapon. However, he arrives just moments after the scientist dies. Who stole the secret formula and killed him?
Morality
Right and wrong are pretty black-and-white, though a couple characters stick their necks out for each other and lie in order to protect.
Spiritual Content
The name of one mentioned (but not drunk) alcoholic beverage is "Satan's Whisker".
Violence
As previously stated, one character is killed. One character play-threatens to poison another with strychnine. Another mentions nightmares she used to have of a woman who had poisoned a bunch of people. One man threatens to "break every bone" of another man's body (he never makes good on this).
Drug and Alcohol Content
Poirot smokes a couple cigarettes and another character smokes once. One woman approves of Poirot's smoking ("gentlemen ought to smoke").
Some alcohols are served but not drunk in excess. One young woman speaks approvingly of "stiff drinks" (none of which make an appearance in the tale).
Some medicinal drugs are mentioned and a doctor describes how potentially deadly they can be.
Sexual Content
One character hints that maybe a couple are going to have a baby, saying "accidents do happen"; she also mocks the Victorian idea of telling children that babies are found under gooseberry bushes.
One woman is described a couple times as a "good-looker" and "beautiful".
Poirot's buddy Hastings finds it "rewarding" to watch a woman sunbathe in the garden. This woman later flirts with him though her affections lie with another man.
Crude or Profane Language or Content
Five or so uses of d**n, one of a**, and two of crikey (which is a derivation of Christ's name). God's name is evoked in exclamations such as "my God" or "for God's sake".
Conclusion
The mystery is an excellent one and is quite clean. The reading is also fairly easy to get through and enjoyable, despite being adapted from a play.