It stars Michele Placido, Claudio Amendola, Alessandra Di Sanzo, Francesco Benigno, Roberto Mariano, Maurizio Prollo, Filippo Genzardi, Alfredo Li Bassi, Salvatore Termini, Luigi Maria Burruano, Gianluca Favilla, Giovanni Alamia, and Tony Sperandeo.

Mery per sempre is set in Rosaspina, a fictional juvenile detention centre (based on a real facility named Malaspina) in Palermo, Sicily, during the 1980s.

He has difficulty in establishing a rapport with the young, hostile students; in particular, Natale Sperandeo (Francesco Benigno), the leader of the group, who is inside for murder, and Pietro Giancona (Claudio Amendola).

Terzi's situation is further complicated when Marilyn Libassi (Alessandra Di Sanzo), a trans prostitute, nicknamed Mery, falls in love with him.

After the death of Pietro, killed during a robbery after a jailbreak, he decides to refuse a well-paid position in the high school to stay with the boys.