The research was done by notable Reformation scholars Theodore G. Tappert and Jaroslav Pelikan who assisted Allan Sloane and Lothar Wolff.

[2] The time frame of the film is 1505–1530: Luther's entrance into St. Augustine's Monastery in Erfurt to the presentation of the Augsburg Confession.

It shows Luther's resistance to the forces of radicalism, and his work to establish and maintain the evangelical movement of his day.

The prior proposes expelling Luther for his restless mind, but Staupitz believes study and a pilgrimage to Rome will help.

Returning from Rome, Luther opines that the common people could more easily find God merciful if the Holy Scriptures were in their vernacular.

Luther meets George Spalatin, who has also left law for the church: in his case to serve Frederick III, Elector of Saxony.

In 1517 Pope Leo X arranges with Archbishop Albert a jubilee indulgence in Germany with Johann Tetzel as the main preacher.

Sales of Tetzel's indulgences fall off, moving Archbishop Albert of Mainz to send Luther's theses to the pope.

In 1519 Andreas Karlstadt tells Luther and professor Philipp Melanchthon he has been invited to Leipzig to debate "our theses."

The Augsburg Confession is presented to the emperor followed by the pealing of bells, and Luther offers a prayer of thanksgiving for God's faithfulness to his generation.

His congregation, young and old, rich and poor alike, sing his hymn "A Mighty Fortress Is Our God" The film received positive reviews from critics.

Bosley Crowther of The New York Times praised the film as "a brilliant demonstration of strongly disciplined emotions and intellects," with dialogue "done with such forceful delivery and in such well-staged and well-assembled scenes that it commands intelligent attention and stimulates the mind.

"[5] Variety wrote: "An artistic achievement of its kind, reflecting careful research and preparation, boasting a magnificent performance by Niall MacGinnis, of London's Old Vic, in the title role, and given reverential, straightforward, honest, sincere treatment, as well as eschewing anything savoring of sensationalism, it is well calculated to stir the enthusiasm of Lutheran and Protestant ministers along with the more devoted laity.

"[7] John McCarten of The New Yorker wrote that every player in the cast "commands attention," and thought that the documentary-like film techniques were used "to good advantage.