Set in Trieste, La Porta Rossa follows the extraordinary case of Leonardo Cagliostro (Lino Guanciale, Time After Time), a murdered police detective who remains among the living as a ghost while trying to solve the mystery of his own death. His wife, magistrate Anna Mayer (Gabriella Pession, Don Matteo) and Vanessa Rosic (Valentina Romani, Gerri), a young medium who can communicate with the dead, have become central to his unfinished business.

Three years after the events of Season 2, Cagliostro remains trapped between life and death after Vanessa left Trieste with Federico. Their relationship has fractured, while Vanessa is now studying parapsychology at a mysterious center in Slovenia. Anna has raised her daughter, named Vanessa in honor of Cagliostro’s wishes, and is preparing to leave Trieste after winning a judicial appointment in Siena. Meanwhile, Paoletto (Gaetano Bruno, The Cases of Attorney Guerrieri) has been promoted and his relationship with Stella has stalled.

The final season begins during a protest against a controversial power plant, when a massive blackout plunges Trieste into darkness. A fatal car crash follows, setting off a new mystery that draws Anna, Paoletto, Vanessa and Cagliostro into separate but increasingly connected investigations. As buried secrets emerge and the supernatural bond between Cagliostro and Vanessa takes on new significance, the series moves toward its final reckoning. For Cagliostro, one question remains above all others: can he finally cross the Red Door?