Leonardo Cagliostro (Lino Guanciale), an impulsive police commissioner not at all inclined to follow procedures and directives dictated by his superiors, is investigating the most difficult case of his career: his own murder.

In fact, Cagliostro was killed during a solitary police action, but, instead of walking through the red door leading to the afterlife, he chose to stay in the earthly world, thus becoming a ghost, to find his killer: this is the only way he'll be able to save his estranged wife, magistrate Anna Mayer (Gabriella Pession), who, according to some visions that Cagliostro has been having since his death, will be murdered by the same killer during the Christmas season.

Cagliostro soon finds out that his killer, most likely, is one of his colleagues, who would therefore be leading a double life linked to the trafficking of a new lethal drug plaguing Trieste, the Red Ghost, that the commissioner was investigating just before being killed.

[3] Originally set in Turin, Piedmont, it was moved to Trieste, Friuli-Venezia Giulia, at the suggestion of director Carmine Elia, who had already shot a movie there in 2003.

[5] To play Cagliostro, the actor rewatched The Sixth Sense and River, and reread Thomas Mann and Fyodor Dostoevsky, likening his character to Ivan Karamazov "who gets crazy when he cannot give himself a logical explanation of the world".

[29] Vanity Fair Italia's Mario Manca wrote that the series, characterized by "intrigues to unravel, pending loves to clarify and a quadrille of twists to cushion", "stage[s] a story of borders, of limits, of universes and of conflicts like we haven't seen in a long time.

The adventures of the Ghost-style ghost played by Lino Guanciale, strong and magnetic even though transparent and in the form of an ectoplasm, in fact, possess something magical, a sort of intrinsic strength".

[30] TVBlog's Paolo Stura believed that "[its] ability to masterfully blend supernatural and crime without damaging none of the two genres is something that must serve as a lesson to those who want to propose stories with a new flavour".

Actors and actresses often move at night in a Trieste whipped by wind and rain, while the dark places of the characters' souls twist in the half-light where nothing is what it seems.

[33] Avvenire's Andrea Fagioli wrote that "the series novelty [...] had already run out a bit with its second season", and that the story "needed to be renewed with less action, more introspection, studies of characters' psychology and new mysteries".

[34] The series premiere of La porta rossa on February 22, 2017 was the most watched program of the night, amassing 3.284 million viewers, or a 13% rating,[35] more than double the network average.