Wade Sowers’s review published on Letterboxd:
When Deborah (Carroll Baker) and her husband Marcel (Jean Sorel) arrive in his hometown of Geneva, Switzerland, to spend their honeymoon, they run into his old friend Philip (Luigi Pistilli) who angrily tells them Suzanne (Ida Galli, billed as Evelyn Stewart), the girl Marcel left behind when he moved to America, has committed suicide and it is his fault. Suzanne was very wealthy, as is Deborah (her mother considers Marcel a "fortune hunter"), and when they visit her estate they find the house is empty, dust is everywhere, with no trace of her family. While wandering through the deserted rooms they hear a piano piece loved by Suzanne mysteriously playing, and receive a phone call threatening Deborah with death to pay for Marcel's crimes. They rush off to the south of France, rent a remote villa, but the music and the calls continue, another character is added when a mysterious neighbor peeps over the fence and enters their home at will, Philip is seen around town, and things are finally brought to a head with one of those double (or triple) crosses that is best not to try and figure out. Ms. Baker gets to wear an absolute riot of colorful 60's costumes, do a bit of dancing, and, as the poster indicates, is comfortable showing herself on screen, usually tastefully covered by pillows and protected by camera angles. The direction by Romolo Guerrieri is serviceable, with lovely shots of Geneva and the coast of France, while the script by the always interesting Ernesto Gastaldi is a bit by the numbers, does not offer any new genre ideas, but might have seemed more original at the time of the film's release. The German Blu-ray (part of "The X-Rated Eurocult Collection #14) is first rate with a solid, colorful picture. It is Region Free and can be watched with the original Italian track and English subtitles.