A party at the villa of the famous actor Sir Charles Cartwright, who recently retired from the stage, attracts thirteen guests. This unlucky number proves fatal for one of them, Pastor Babbington—he suddenly dies after taking a sip from his cocktail glass. Is it an accident or deliberate murder? The great detective Hercule Poirot, who is among the guests, takes up the investigation. However, chemical analysis reveals that the deceased's glass contained no poison. And, what puzzles Poirot even more, there is absolutely no motive for murder. However, the detective is convinced that an accident is out of the question...