The Bird with the Crystal Plumage works because of its simplicity. Not only did Argento begin his directing career with this film, he also wrote it, and the story he came up with is fabulous. It really has that feel of a classic murder mystery, with all the classic plot elements and devious devices you love from movies like it. Not that I'm advocating a remake or anything, but if someone were to do something similar today, they really wouldn't have to change a thing about the major plot points - my sign of a true classic. The only thing I am a bit iffy on is how involved in the case Inspector Morosini allows Sam to be. Granted he kind of does a better job than the police do, but it's still the principle of the thing.
I was surprised to find a bit of a humorous element in some scenes. There's a cute little relationship scene between Sam and Julia when she gets mad at him and starts throwing things, and he just laughs and goads her even more. That kind of realism is always fun to see. But obviously the best humorous scene is when Sam goes to visit the painter, and finds him to be just as eccentric as painters are often portrayed as being. Although I don't completely love this scene because eating kittens is so wrong. So very, very wrong. There are also some moments of true suspense that I loved, such as when the killer is trying to get in the apartment when Julia is there alone. My favorite part, though, is when Sam walks into the darkened room of the killer's, not knowing or seeing poor Julia tied up and gagged on the floor. The revealing shot is perfectly framed and a great shock for the audience.
Sometimes I think it's best to judge a director on some of their first efforts moreso than their later films. The Bird with the Crystal Plumage is a more than solid directorial debut for Dario Argento, who obviously had talent straight out of the gate. It's a perfectly written and executed mystery thriller that gets all the beats right. No doubt another favorite has been born.