Malasaña neighborhood, Madrid, Spain, 1976. While political turmoil ravages the streets all over the country, the Olmedo family arrives in the big city and settles into their new apartment. They soon discover that they are not the only ones roaming its corridors.

Teenager Bianka is the coolest babysitter in town, until one night, it is discovered that she belongs to a satanic sect and needs to sacrifice a young virgin.