Filmmaker Michael Schwarz had shot two-thirds of his documentary “Muhammad: Legacy of a Prophet” when terrorists attacked the United States.

The events of Sept. 11, 2001, and the way they affected American Muslims made Schwarz’s film more important than he ever had imagined.

The two-hour documentary “Muhammad: Legacy of a Prophet” will air at 9 p.m. Wednesday, Dec. 18, on Maine PBS. It interweaves the story of how a man who could not read or write established the new religion of Islam amid interviews with American Muslims and Islamic scholars.

While the film tells in great detail the story of Mohammed, sometimes spelled “Muhammad,” and the spread of the religion, this section of the film is visually repetitive and stagnant. Schwartz was unable to show any images of the prophet or his family or closest associates. To discourage idolatry, Mohammed asked Muslims not to create such images, and, although some do exist, most Muslims consider them offensive.

The interviews with Muslims living in the United States are the heart and soul of this film. They include a second-generation American Muslim who works as a nurse, a convert to Islam who is one of the New York firefighters whose life was transformed by the terrorist attacks, an Arabic calligrapher who elegantly copies sections of the Quran on parchment, and an iman, or lay leader, of a mosque. The documentary is narrated by actor Andre Braugher, who costars in “Hack” on CBS.

The film takes pains to explain the prophet’s efforts as peacemaker and warrior as well as the treatment of women in Islam. Schwarz puts the major tenets of the religion in historical and sociological perspective in a way that is at the same time fascinating but visually tedious.

In the end, it is Americans talking about their relationships with their faith that comprise the most revealing, compelling and enlightening sections of the film. The fact that all of them live in large metropolitan areas is the film’s major flaw. Muslims worship in small communities like Bangor and face, perhaps, more difficult struggles because of their isolation.

On the whole, “Muhammad: Legacy of a Prophet” sheds light on a religion that is still sheathed in mystery and misunderstanding for many Americans. It is “must see” television for anyone curious about lifting the veil and learning more about the world’s fastest-growing religion.