FRANK GIBNEY was old and sick and a little more than a month away from dying. But he was filled with righteous anger, and he had some things to say. He told his son, the documentary filmmaker Alex Gibney, to unplug a noisy oxygen machine and to grab a video camera.

The older Mr. Gibney, a journalist and scholar who died in April, had served as a naval interrogator in World War II. In a moving statement that serves as a sort of coda to “Taxi to the Dark Side,” a new documentary about the Bush administration’s interrogation policies in the post-9/11 world, he said it had never occurred to him to use brutal techniques on the Japanese prisoners in his custody.

“We had the sense that we were on the side of the good guys,” Frank Gibney said, seething. “People would get decent treatment. And there was the rule of law.”

There would seem to be an enormous distance between the Bagram Air Base in Afghanistan, where the central events in “Taxi to the Dark Side” take place, and Enron’s headquarters in Houston, where the machinations of white-collar criminals brought down the giant energy company and became the backdrop for Mr. Gibney’s entertaining 2005 documentary, “Enron: The Smartest Guys in the Room.” But Mr. Gibney said the two projects have common themes.