The Bulldog Drummond-type plot of Cat Among the Pigeons requires some considerable suspension of disbelief, but this film is so beautifully shot, so sumptuously acted, so gorgeously sly, that it is just one hugely enjoyable romp. Of course the murder victims are awful people that the world can do without; of course the good guys are all noble and articulate and upper-class, and the whole is set in a fabulously soft-focus England replete with a jolly-hockey-sticks girls school, proper school marms, impoeccable manners, afternoon tea from delicate china, exotic jewels, foreign princesses, handsome spies, very civilised shoot-outs, a suitably grumpy police inspector, a wonderfully dramatic expose and the incomparable Poirot.
It all hangs together in a most satisfactory way, with one huge glaring plot point....
Everyone at the school has a dark secret. And so the entire film comprises the police, several members of the British Secret Service, and Poirot himself trying to work them out. Yet the gym teacher manages to dig up everyone's secrets entirely on her own! How come she managed it so easily, while the others needed files, reports, background investigation, interviews, the finest minds in English espionage, and considerable help from Poirot to reach the same conclusion?