Para ayudar a Marcos a superar sus inseguridades y problemas personales, los tres deciden embarcarse en una relación poliamorosa o ménage à trois . Lo que empieza como una experimentación libre y apasionada, donde comparten su amor por la pintura y su intimidad, pronto se ve amenazado por:

Just dug up a gem from 2009: ( Cardboard Castles ).

If you're into intense Spanish dramas about art, friendship, and complicated love triangles, this one stays with you. Directed by Salvador García Ruiz, the film follows María, Jaime, and Marcos — three art students whose relationship blurs the lines between creativity, passion, and jealousy.

The story follows María José (Adriana Ugarte), a shy and talented painter from a humble background, who becomes entangled with two charismatic yet troubled fellow students: Jaime (Nilo Mur) and Marcos (Biel Duran). What begins as a bohemian friendship evolves into a volatile ménage à trois. The film’s title – "Cardboard Castles" – serves as a metaphor for the fragile, illusory structures of passion and youth that are easily collapsed by jealousy, economic hardship, and sexual awakening.

: The title serves as a metaphor for their relationship: while it feels solid and revolutionary at the time, it possesses the "inner fragility of a cardboard castle".

What begins as a clandestine romance evolves into a cohabitation that defies social norms. The three characters attempt to live together in a "paper castle"—a fragile construct of bohemian ideals and shared affection that is destined to collapse under the weight of jealousy, societal judgment, and internal neuroses.