PBS's "Independent Lens" offers an interesting if not exhaustive look at the Jehovah's Witness faith in "Knocking" (10 tonight, WQED). The hour-long documentary skims over the founding of the faith near Pittsburgh in 1870 by C.T. Russell, but offers a decent history of the religion and what its members believe, but these sections would be improved if more time was devoted to them.

PBS Seth Thomas (left) and his father, Ralph, in PBS's "Knocking."

Writer/director/narrator Joel P. Engardio, who grew up in a Witness home but never joined the church, offers a sympathetic view of the religion and two families who practice it capture more of his attention than the religion's history. The most compelling story follows a 23-year-old man who needs a liver transplant, but Jehovah's Witnesses don't believe in accepting blood transfusions.

"Knocking" shows how the beliefs of the organization have had an impact on medicine (142 hospitals in American now offer bloodless surgeries), civil rights and in legal cases that have reached the Supreme Court.

A study/discussion guide created for "Knocking" offers more detail than the film and does a more concrete job at showing the links between Jehovah's Witnesses and secular society, but the film itself offers an OK introduction to the faith.