Robert McCall finds himself at home in Southern Italy but he discovers his friends are under the control of local crime bosses. As events turn deadly, McCall knows what he has to do: become his friends' protector by taking on the mafia.

In early 1860s New York, Irish immigrant Amsterdam Vallon is released from prison and returns to the Five Points, seeking revenge against his father's killer, William Cutting, a powerful anti-immigrant gang leader. He knows that revenge can only be attained by infiltrating Cutting's inner circle. Vallon's journey becomes a fight for personal survival and to find a place for the Irish people.

Love, business, anxieties, friendships, feuds, and resentments paint the picture of the main story, that of a group of criminals who for nearly fifteen years, from 1977 to 1992, cherished an illusion: that of conquering Rome. The Lebanese, Freddo, Dandi, Patrizia, and Commissioner Scialoja are some of the characters inspired by the true story of the Magliana gang. As stated by Aldo Grasso, the first season of the series gives more space to the crime scene, that is, the criminal exploits of the Magliana gang, while the second season delves deeper into the "behind the scenes" of the crime: thus, the gang's repositioning after a key plot event, and the effects and questions this has provoked in the protagonists' consciences.

Two linen fabric dealers with their shops close to one another, battle against each other for more and more costumers. Umberto constantly loses clients because of the tough competition brought by Leone, who offers the best prices in the neighborhood. But they leave differences aside when the rise of Fascism places Anti-Semitic politics which rigidly control business like the one conducted by the Jewish Leone, and those new regulations are viewed by Umberto as completely unfair. The long rivalry soon becomes a great friendship.

Carabinieri's lieutenant Duilio Cordelli is in charge of investigating fake banknotes traffic. He discovers that a 60 billion lira bank robbery is linked with his case. Things get more complicated when the main suspected, Lorenzini, is killed. Moreover, Cordelli villa is blown up and the evidence points to the conclusion the whole case could be solved only by flying to London.

A police inspector is called to Milan to investigate a murder case since he grew up in the same ghetto as the suspect.

When his destituite widowed sister-in-law—whom he had never stopped harbouring feelings for—and her ne'er-do-well son come to live with him after World War II, a mentally-ill farmer who spends all his time destroying unexploded ordnance scattered across the countryside finds a new purpose in his lonely life.

Michele Casali is a middle-class professor in Fascist Italy who teaches at the same high school attended by his only daughter, Giovanna. A shy and sensitive girl, her insecurities are only magnified by Michele's overprotectiveness—reaching a point of no return.

In Rome, the Cassamortari are people who work in the funeral business. The Pasti family's agency was founded by Giuseppe, who is willing to do anything to turn a corpse into money, preferably in black.

Lino and Chicca are an aging, childless middle-class couple whose life is disrupted after he's diagnosed with Alzheimer's disease.

Stella works in a restaurant in Rome. She feels frustrated about her life. In spite she has turned 40, she dreams of a film career.

Giorgio is a young talented boxer who lives with his mother and dreams to became a champion.