The film is famously inspired by the 1991 Vallecas Case in Madrid, involving Estefanía Gutiérrez Lázaro.
While the surface plot follows a girl who inadvertently summons a demon during an Ouija board session, deeper readings suggest the "demon" is a manifestation of her internal turmoil:
: At the climax, it is revealed that Verónica herself was the one harming her siblings while under the belief she was fighting an invisible entity. The fingerprints found only on the board by police support a psychological interpretation. The "Vallecas Case" (True Story Context)