Poirot vs the Stymphas of Hercules

Poirot, the famous detective wants to retire, but he tells himself he has to go with a big bang. Three last cases, he tells himself. A woman comes to his house and talks about Stymphas. This can't be one of the Big Three, can it? Then he remembers who also fought with these creatures: Hercules himself! This story is based on A. Christie story and was written for a huge Dutch Poirot contest.