Deputy Commissioner Vanina Guarrasi and her trusted team investigate the suspicious discovery of some pills in the tubs of a famous ice cream shop, an unusual and curious fact that turns out to be the premise of a much more complex crime. Even Vanina's private life resembles a puzzle: on one side there is Manfredi, the romantic doctor who tries to make a dent in her heart. On the other, the anti-mafia magistrate Paolo Malfitano, the great love of her life, who however she seems to want to leave behind.

The black sand of Etna submerges Catania and Vanina is forced to deal with the end of her story with Paolo, while a corpse resurfaced from the past demands her attention. In an uninhabited villa, the mummified corpse of a woman is found: it is Maria Cutò, a prostitute who died fifty years earlier. Vanina discovers that Gaetano, the man she was supposed to run away with, had also been killed there, perhaps killed by the mafia. But what is the truth? Is it pure coincidence? The case had been solved quickly at the time but the policewoman discovers a terrible past.

A new case brings Vanina and Manfredi back together. It was the doctor himself who saw two suspicious men throwing a heavy suitcase soaked in blood into the sea, so Vanina will find herself investigating the murder of a girl that took place in a villa. The victim is the lawyer Lorenza Iannino, of whom no other traces can be found. The villa turns out to be owned by the lawyer Elvio Ussaro, a shady prince of the bar, but a macabre discovery will overturn the course of the investigation. Meanwhile, just when Vanina opens her heart to Manfredi, a family commitment brings her face to face with Paolo again and the unresolved issues of their relationship.