The third Lenzi giallo I've watched after having attended screenings of ORGASMO (1969; incidentally another of his collaborations with star Carroll Baker) and SPASMO (1974) during the Italian B-movie retrospective at the 2004 Venice Film Festival; they're not the best examples of the genre by far, but neither are they among the worst.
I recall ORGASMO being pretty complex, while SPASMO was weird without being especially compelling (though I did watch it as part of an all-night marathon that ended at 8:00 and where the screening of Lenzi's film was interrupted a couple of times because of trouble with the print!). As for the film in question, it's basically a retread of Robert Siodmak's noir-ish masterpiece THE SPIRAL STAIRCASE (1946) - which Lenzi himself had singled out as his favorite film during one of the many Press Conferences he gave (along with colleagues Sergio Martino and Enzo G. Castellari) during the Festival: Baker plays a mute, the main setting is an upper-class household in a small rural town, the climax occurs during a thunderstorm and, of course, there's a serial killer on the loose! The narrative also takes in drug addiction and devil worship, but these emerge as mere red herrings.
Still, for a giallo, it's pretty bloodless and, to be honest, its attempt at psychology - demonstrated by frequent abrupt cutting in which Baker has flashes from her past, as well as the various victims at their moment of death, and the possible perpetrator - is not only unconvincing but becomes a repetitive device with little purpose (given the final revelation)! As a matter of fact, this particular twist was re-used in SPASMO; still, the obligatory explanation offered here is a little weak but, then, this form of coda seldom worked within the confines of the giallo subgenre! Besides, the score is undistinguished and the casting merely okay: Georges Rigaud (as Baker's ageing uncle, who has a heart condition which he ultimately uses to his own advantage!), Eduardo Fajardo (as a sinister-looking chauffeur), Evelyn Stewart, etc.
