You say Argento, I say sub-Hitchcock.
The story concerns a piano teacher played by David Hemmings, who witnesses the murder of a psychic woman thar lives one floor beneath him, and for some reason then decides to devote all his time to tracking down her killer. This of course makes him a target of the killer as well, and he teams up with a feisty female reporter to engage in an investigation like a pair of amateur detectives. Deep Red adheres closely to all the tropes of giallo: a mystery killer in a long coat and black gloves, a series of increasingly staged, brutal murders - all of it overstylized to the point where it becomes nearly comical. You can almost feel Argento slowly growing bored with the toolbox he’d been playing with for four films now, although certain scenes display a life of their own (such as the infamous mechanical doll that was on so many VHS covers), pointing to where he would go next to spectacular effect in Suspiria. He puts his all into each and every kill, and his ever-moving camera and the film’s explosive (and completely ridiculous) ending keep the energy and the tension high throughout, but you can’t help but get the feeling watching the film now that this was ground Argento had already covered, spinning his wheels until he’d found something new.