Based on the 1981 horror novel of the same name by English writer Ramsey Campbell, it follows a mother who receives a phone call from her believed-deceased daughter five years after her apparent occult-related ritualized murder, uncovering a nefarious cult preoccupied with the metaphysical aspects of corruption and evil.

The Nameless proved to be a box-office success, and has been credited for spearheading a series of major studio horror films produced in Spain in the 2000s.

The parents of missing six-year-old Angela Gifford, local editor Claudia and her British husband Marc, are duly notified.

It was first documented in Liverpool in 1962 and led by Argentinian expatriate Santini, whose scientific approach to ponerology went far beyond the activities of his original London occult circles.

It contains a snuff film featuring a young female victim, followed by surreptitious footage of Claudia visiting the derelict clinic.

He speaks to Claudia in riddles, obliquely mentions his acquaintance with Angela, recounts his confinement in a cobalt capsule in Dachau, and extols evil and suffering as sources of enlightenment.

It soon becomes apparent that Santini's followers are still active; upon returning to her apartment, Claudia and Massera find Toni butchered, along with another cryptic message.

Writing on the film's ambiguous conclusion, Jessica Balanzategui notes that narrative renders it impossible to discern whether or not the Angela that Claudia meets in the final scene is actually her daughter, leaving the audience "trapped in a perceptual gap incarnated by the child's subversive ambiguity," and the character of Claudia "forever entombed by the any-space-whatever of traumatic loss... a desolate future in which [she] will endlessly be tormented by a chain of "nameless" children posing as Angela.

[6] In the 2011 book Directory of World Cinema: Spain, Lorenzo J. Torres Hortelano named the film "one of the most ambitious genre debuts of the last 20 years, supported by solid acting and the cold, murky cinematography of Xavi Giménez.

Licensing the title from Miramax, Echo Bridge Entertainment re-released the film in the United States on DVD and Blu-ray on May 10, 2011, and on March 10, 2013, respectively.

[8] In Spain, Filmax issued a special edition DVD and Blu-ray combination set on 6 July 2017, which contains both the original Spanish audio as well as the English-dubbed version.