The Cat o' Nine Tails is an improvement over Argento's Bird with the Crystal Plumage, but not by much. Similar to TBWTCP, TCONT is a giallo where a civilian is playing detective - maybe a little more plausible this time around, for reasons I will cover in a moment. The movie starts with Franco, a blind man, and his... adopted daughter - I think. A series of crimes lead Franco to seek the assistance of Carlo, a reporter, in solving the mystery. As before, someone who is not involved in law enforcement putting themselves in harm's way to solve a murder case is just ridiculous; though, at least, this time we're dealing with a reporter, and a former reporter, so they may be slightly more accustomed to snooping around to get a story, but that does not make them Batman or Daredevil.
The movie is almost two hours long, and it didn't need to be. It's a very simple story, laden with more characters than necessary - for example, Carlo, and Franco could have just been combined; the only reason Franco was there was because of his "daughter."
[spoiler]So, the killer is Casoni. Okay. By the time that was revealed, I had forgotten who he was. Turns out he has an XYY chromosome, which - according to the scientists in this movie - means he is prone to murder. If this information was found out, he'd lose his job. Solution: murder people. Problem solved. If that sounds dumb as fuck, that's only because it is.[/spoiler]
Don't go into this looking for horror. It's 99% mystery, with limited kills - very tame.