Fruit of Paradise (1970)

In the garden of a pension, Eva and her husband Josef are enjoying a siesta. Here, they meet with the lonesome, mysterious-looking Robert. During play, a key falls out of Robert's pocket. The curious Eva picks it up and sets off on an expedition. In Robert's room, she finds a briefcase soiled with mud, which Robert had forgotten by her parsley patch before, and in it, a date-stamp. Soon afterwards, she learns that another victim of an unknown murderer of women has been found, with a number and date stamped on her forehead. Eva concludes that the murderer must be Robert.