Three out of four ain't bad - the first three Poirot stories are each a delight, from thefts to murder. They're short - Poirot sometimes barely has anything to go on at all when he makes his deductions, but each of them addresses a very particularlized view of Englishness, which is Christie's forte.  The last one is a bit of a dud - not much happens and Poirot certainly does little enough.  The quality of the previous ones are among the best of the best, however.