12 DAYS OF HALLOWEEN!
I really wasn't planning to watch two Dario Argento movies in the same week, (Suspiria being the other) but that's the way the tables often turn going through this list at times. This film does have a serial on the lose and contains its share of violence, but it is primarily a police procedural with a fish out of water American caught in the middle of a murder investigation and gets too heavily involved in trying to help solve it. The Bird with the Crystal Plumage is a pretty good thriller at that and doesn't play its plot hands too quickly.
Additional casting notes: It was great to see Tony Musante pop up as the lead in this movie. I remember Tony mostly from his one season as Toma, the master of disguise cop TV show from the early 70's. Tony left Toma after one season and the show was changed into Baretta and became an even bigger hit.
It's was also great to see leading lady Suzy Kendall (To Sir, With Love) in anything. Truly one of the great beauties of the 60's.