A businessman from Barcelona is murdered in the town of Canfranc, near the French border, with a gunshot to the head. The police arrest an immigrant from Somalia, who is caught with the gun inside the house. The corpse has a wine glass with the word "Bacchus" tattooed on its abdomen.

Drago, the public defender, who is called to defend the Somali, suspects that the accused is innocent and that in reality he has been framed for the crime. And, drawing on his experience as an ex-cop, he embarks on an adventure through Barcelona, trying to find out who was the man who was murdered and why someone would want to kill him.

In the first inquiries he discovers that since 2016, every year, without fail, someone dies with a tattoo identical to the one on the man from Canfranc. And, in every case, an immigrant has always been arrested as the perpetrator of the crime