Ominous music and lush cinematography override a sparse script to create a Jack-the-Ripper type thriller, which is deeply introspective, moody, and haunting.
Indeed, the script can be treacherous if used to try and solve this whodunit puzzle, which is best handled by removing psychological assumptions rather than by piecing together logical clues. Even so, the murder mystery plot is to some extent illogical.
The strength of the film though lies in its suspense, which is almost unbeatable. It rivals any of Hitchcock's works, to which it is repeatedly compared. The scene showing a knife chipping away at a wooden door is reminiscent of, and more frightening than, scenes showing bird beaks chipping away at a farmhouse door in Hitchcock's "The Birds".
I like the film too because it is so nostalgic. The reel-to-reel tape recorder and dozens of other props and visual cues, the references to philosophy and mysticism, the Morricone film score which at times sounds like the film scores from his spaghetti Westerns, all conspire to transport the viewer back to the Age of Aquarius.
The acting is fine. Tony Musante, Suzy Kendall, and Enrico Salerno are perfect for the roles they play.
This is one scary movie. Minor flaws notwithstanding, "The Bird With The Crystal Plumage" is top-notch entertainment for fans of suspense thrillers.