The plot is based on true story on an undercover agent who infiltrated ETA under the name 'Aranzazu Berradre Marín' and managed to dismantle the 'Donosti' cell [es].

[1][2][3][4] Undercover is a Bowfinger International Pictures, Beta Fiction Spain, Esto también pasará, and Infiltrada LP AIE production, with the association of Filmfactory Entertainment, the participation of Movistar Plus+, Atresmedia, EiTB, and Crea SGR and backing from ICAA.

[13] By February 2025, the film had grossed around €8.5 million at the Spanish box office.

[16] Rubén Romero Santos of Cinemanía rated the film 4 out of 5 stars, writing that it "takes off and excels when political terrorism is mixed and confused with gender terrorism".

[17] Juan Sardá of El Cultural rated the film 4 out of 5 stars, writing that it "hooks like the best thrillers and boldly and knowledgeably portrays a recent historical era that today seems hard to believe".