Poirot solves a "Problem at Sea" while on a cruise with Hastings. Unfortunately, the audience figures it out, too, probably ahead of him.
Poirot and Hastings are on a cruise around the Mediterranean, with Hastings acting as a sort of social director. An unpleasant woman, Mrs. Clapperton, is found murdered in her stateroom. Since everyone hated her, there should be plenty of suspects. Just one problem. Many of them were off the ship at the time.
Poirot has to solve the problem. By the time he gathers everyone together to expose the murderer, we've been in on it for some time. The how, however, I found both amusing and interesting. So it wasn't a total loss.
This series spares no expense on production values, which, have others have mentioned, are marvelous. It doesn't matter if it's a weaker story. David Suchet is always wonderful to watch, as is Hugh Fraser as Hastings.