In a Dream, which screens at SF DocFest over the next few days (details below), is a film about the mosaic artist Isaiah Zagar, who has become an icon in South Philadelphia for the massive scale and extent of the mosaics he has created there. They include, by his description, about “a hundred murals” and “seven buildings, top to bottom, inside and out.” His best-known work is Philadelphia’s Magic Gardens, which represents the transformation of two derelict buildings into a labyrinthine complex that covers half a city block with winding mosaic-covered passageways and sculptures.

Zagar’s mosaics are bright, colorful, and complex, rich with a celebratory spirit towards physicality and sensuality. But the surface cheerfulness of these mosaics belies the deeper obsession and the narcissism that makes such vast, intricate works possible in the first place, and Jeremiah Zagar — the director of the film and the artist’s younger son — uncovers that darkness here with unrelenting economy. All the father’s past secrets rapidly come out in the open, culminating when one of his most shameful episodes plays out right in front of the camera: his self-centered pursuit of “passion” with his assistant, which ends with a brief separation from his wife Julia, right when their oldest son is separated from his own wife and having drug problems.

Jeremiah describes the moment: “I went home to film my parents as they picked my brother up from rehab. The stress from the situation boiled over, and my father suddenly admitted [the affair] to my mother and me … that same night, my parents separated for the first time in 43 years.” Isaiah’s admission is made directly into the camera, and it’s a moment of remarkable drama. Amazingly, Jeremiah retains his composure — he coughs and the handheld camera shakes for an instant, but that is all — and he goes on to capture every instant of what ensues. “I shot 16 hours that day and hated myself for every minute of it,” he writes. Fortunately, Isaiah realizes he has made a big mistake quickly enough. Soon afterward, he goes to stay with his assistant and, as he confesses, “within minutes, my whole being started to rebel. My whole being.”

In the end, he reconciles with Julia, and the film has a brief epilogue, highly effective in its simplicity, that shows how, after a time of healing, the two simply picked up their life together and continued on into the next adventure.

For all the darkness that Jeremiah reveals, it’s an affectionate film. He shot his footage over the course of seven years, filming “whenever something significant happened,” and he describes the result like this: “what started as an exploration of my father’s life has exposed the secrets of our entire family. But I don’t think that’s a bad thing. … We know now how imperfect we really are, but also how much we need and love each other.”

The film is highly recommended. In a Dream screens at the Roxie this Sunday, October 26th at 2:45 PM, and Tuesday, October 28th at 9:30 PM. It will also screen at the Shattuck next Sunday, November 2nd at 2:45 PM.