This is the second Spanish incursion for Larraz in the middle of a period in the early 70s when he was mostly shooting in the UK. In fact, the film shares some plot points and mood with the much better "Symptoms" that he shot the same year in England. For whatever reason the Spanish films that I have seen of Larraz don't have the same creepy and attractive atmosphere as the ones that he films outside his country and this is another good example.
Review of Emma, puertas oscuras
