The guts of the film, adapted from Charles Brandt’s book “I Heard You Paint Houses,” concerns the question of whatever happened to the powerful Teamsters Union head Jimmy Hoffa, who suddenly disappeared in 1975. He had to be assumed dead, and various stories have arisen about his demise and claims that his body was discovered.

Scorsese’s film builds to a specific answer about Hoffa, with leaving nothing to the imagination in the screenplay by Brandt and Steven Zaillian. The entire story unfolds from a narration by a character named Frank Sheeran, the Irishman of the title, and played by Robert De Niro in a devastatingly convincing performance. ( Sheeran was a real life character who claimed information about Hoffa.) Here De Niro as Sheeran not only reports on his life but is the conduit for the film’s searing look at Mafia crime that raged in the United States, with various real-life assassinations grimly recorded. Scorsese has a neat touch—every so often when a character appears a brief obituary reporting on the time and manner of death is posted.

Hoffa is portrayed by Al Pacino in a blistering acting turn that stresses Hoffa’s arrogance, insistence on power, his making enemies and his activities that landed him in prison for a while. Upon his release, he bids to resume the power he held before prison in the face of opposition. Pacino’s Hoffa is a full-bodied character who dominates a major portion of the film.

But it is through Sheeran’s story that we get the corrupt wielding of power that keeps people in line. When he meets Joe Pesci, another Scorsese stalwart, as the all-powerful crime boss and fixer Russell Bufalino, the story line of mob rule begins to develop, with Sheeran going along as a cooperative player.

The film is also replete with dark humor, family depictions and complications. One of Sheeran’s daughters, from childhood on, looks disapprovingly on her father, as if she knows that he is corrupt and resents it. We meet a host of characters through the film, including wives, gangland pals, victims, union men, cops, government men, bodyguards, and young people tending to Sheeran in old age who don’t even know who Hoffa was.

The film rings with authenticity both in settings and characterizations. De Niro as Sheeran maximizes the sadness of his handicaps as he is elderly and frail, but given all of his contributions to corruptness, it is difficult to feel compassion for him even though some of what he has done was against his will.

Details about the period in which the story unfolds are included, as for example,the Bay of Pigs fiasco and the assassination of President Kennedy. Hoffa’s hatred of Kennedy’s brother, Attorney General Robert Kennedy, is dramatized. Curiously, the film doesn’t include Robert Kennedy’s assassination.

But with everything that is included, Scorsese’s “The Irishman” emerges as a grand epic that should hold a place among the best of the director’s films. It is a powerhouse of a movie-going experience, and you will find special strength in the acting of a huge cast that complements Scorsese’s directorial savvy and includes, among others, Harvey Keitel, Bobby Cannavale, Ray Romano, Stephen Graham and Anna Paquin. The film reflects excellent work by cinematographer Rodrigo Pieto, production designer Bob Shaw and editor Thelma Schoonmaker.