During the Great Depression, various bank robbers and other outlaws have become folk heroes due to public distrust of financial institutions and the law.

Following the Kansas City Massacre in June 1933 in which several law enforcement offers were killed brazenly in broad daylight, FBI field office chief Melvin Purvis decides to personally hunt down the men he deems responsible: Charles Arthur "Pretty Boy" Floyd, Lester "Baby Face" Nelson, George "Machine Gun" Kelly, "Handsome" Jack Klutas, Wilbur "Mad Dog" Underhill and John Dillinger.

During a meeting with fellow FBI agent Samuel Cowley, Purvis makes it clear he seeks personal vengeance and that he's willing to use extralegal measures if necessary.

Dillinger is in the midst of his criminal career, accompanied by Homer Van Meter, Harry Pierpont, Charles Mackley, and others, and is very boastful about his exploits.

While lying low in Arizona with the rest of the gang, Dillinger is captured by the local authorities and transported to Crown Point, Indiana.

While imprisoned there, Dillinger makes a daring escape after carving a bar of soap into the shape of a gun and fooling the guards into releasing him.

He takes a fellow prisoner Reed Youngblood with him, and they eventually meet back up with the gang, including new members Nelson and Floyd.

The gang's luck runs out following a bank robbery in Mason City, Iowa, which leads to a violent shootout ending in Youngblood's death and the wounding of another member.

During this chaos, Pierpont, Nelson, Van Meter, and Floyd are all hunted down by either federal agents or local vigilantes and summarily killed.

Hoover's message is delivered by voice actor Paul Frees after the end credits have stopped rolling: "Dillinger was a rat that the country may consider itself fortunate to be rid of, and I don't sanction any Hollywood glamorization of these vermin.

"Credits from American Film Institute:[5] In the early 1970s, John Milius was one of the most sought-after screenwriters in Hollywood, selling his scripts for Jeremiah Johnson and The Life and Times of Judge Roy Bean for record sums.

Much use of various local landmark buildings was used in the filming from Jet, Nash, Jefferson, Hunter, and Enid in northern Oklahoma, to Ardmore, Dougherty, the Chickasaw Lake Club which served as Dillinger's "Little Bohemia" Wisconsin hideout, and the old iron truss bridge near Mannsville in the south.

[12] Roger Ebert of the Chicago Sun-Times awarded three stars out of four and called it "the film, we may speculate, that John Milius was born to make: violent, tough, filled with guns and blood."

"[15] A. H. Weiler of The New York Times wrote, "'Dillinger' does capture the look of the nineteen-thirties, but its violence dominates the scene and the players, who remain largely undefined figures on a bloody landscape.

"[16] Gene Siskel of the Chicago Tribune gave the film two-and-a-half stars out of four and wrote that it "repeatedly copies the spirit, and a few scenes, of 'Bonnie and Clyde.'

"[17] Variety wrote, "Necessarily episodic, it loses somewhat in a lack of straight storyline, but there's sufficient fast action of the gangster type to satisfy this particular market.

"[18] Kevin Thomas of the Los Angeles Times wrote, "The idea that the Depression could create folk heroes out of gangsters was expressed with such freshness and imagination in 'Bonnie and Clyde' that it seemed like a revelation.

In 'Dillinger' (at selected theaters) writer John Milius, in his feature directorial debut, attempts to make the same point, but because it has already been made so powerfully it comes out like mere repetition.

[23] Shortly before the release of the film, following the era's customary timing, Curtis Books published a novelization of the screenplay by Edward Fenton (1917–1995) by his tie-in pseudonym, "Henry Clement."