Most of the notorious serial killers we hear about seem to have been from the United States, and fictionalized accounts of their crimes are well represented on television. But that doesn’t mean these types of crimes weren’t happening abroad. The new four-part series “The Monster of Florence” provides a fictionalized retelling of the real investigation into seven double murders that were committed between 1974 and 1985 in Florence, Italy, targeting couples who were on lovers lanes or in secluded countryside areas. The perpetrator, and motive, remains unknown. Streaming Wednesday on Netflix.