Here's a short Italian lesson: 'giallo' means 'yellow', and it is often used to describe a certain type of crime novel sold in Italy, for their yellow covers, as well as the crime novels that spun off from those paperbacks. Here's where it gets a bit confusing however, because ''Giallo'' films very soon mutated into horror films that are called ''thrillers'' in Italy, and ''giallo films'' in the english-speaking world. So, when we talk about ''giallos'' over here, we're incorrectly pluralizing giallo and talking about movies that aren't gialli anyway.
But, whatever we call these things, Dario Argento is an undisputed master of making them. The Bird with the Crystal Plumage, from 1970, is a well-constructed mixture of Hitchcockian mystery, slasher mayhem, art world hipsters, and a killer in a black vinyl raincoat. The story is about an American who witnesses a near-murder in an art gallery and becomes the target of a woman-killer. Some of it falls apart with close-inspection: there are places in which the mystery could have, logically, been solved a lot earlier. And a few of the plot twists are just plain weird- always a danger with Argento movies.
I still liked it because it was fast-paced, relatively plausible, had a score by Ennio Morricone (who must've scored every Italian production in the 60s), and featured a killer with a bad-ass, black, shiny, vinyl raincoat. One upon a time, Argento was sort of a kinkier, baroque, pop-art, Italian version of Hitchcock, and bless him for that.