The plot concerns the disappearance of 3 girls—Sandra, Elena and Malena—in 1992 in the fictional Valencian coastal town of "Almanzora de la Vega".[1][2][3][n.

Created by Fernando Gonzalez Molina, Ruth García and David Oliva, cited inspirations included the works of Steven Spielberg and series such as V, Verano azul and Compañeros,[13] although it was already likened to Stranger Things soon after the announcement of the project.

Shooting locations in the province of Alicante included Benidorm, Altea, Xàbia, Santa Pola, Calp, L'Alfàs del Pi and the Natural Park of Serra Gelada [es].

[12] Additional footage was shot in other locations such as Alhama de Aragón (Zaragoza), municipalities in the Valencia province and the Madrid region,[20] and the Centro Nacional del Vidrio in La Granja (Segovia).

[10][17] In June 2021, The Mediapro Studio reported that the production crew had begun filming of season 2 on 17 May 2021 in Begur (Girona), with Fernando González Molina returning as director.