San Francisco director Rob Nilsson casts his digital videos from an acting workshop he founded called the Tenderloin Ygroup, some of whose members are homeless people or inner-city residents. They improvise many of their lines, and because their performances lack calculation, they evoke the rough and tenuous quality of life on the periphery: people interrupt each other, repeat themselves to distraction, and explode in rage, yet their arguments are weirdly pointless. Nilsson will attend the Saturday screenings of this trilogy's components (the general title refers to the time each story begins) and lead discussions afterward. Stroke (2000, 97 min.), the best of the three, opens with an aging poet suffering a stroke; barely ambulatory and unable to speak, he's taken in by a neighbor in his SRO hotel. A superbly revealing confrontation between his caretaker and an escort-service operator over a small loan conveys the circularity of their conflict but ends with two hustlers recognizing and acknowledging each other. The video is nowhere near as seductive or entertaining as a Cassavetes film--and arguably the better for it. In Singing (2000, 75 min.) a man flees a candlelit encounter with his girlfriend of 20 years, who no longer turns him on, and plunges into a night of increasingly threatening encounters. Many scenes seem improbable--a man menacing the protagonist with a knife, threatening to rape him; a sudden kidnapping in a taxicab--but the story's descending arc eloquently poses the question of whether apparently well-ordered middle-class lives are that far removed from the chaos of the streets. Least impressive is Scheme C6 (2001, 97 min.), about a young man from a rich but shady family who chooses a life of petty crime after hearing rumors that his father had his brother murdered. The actors' riffs provide some good moments, like the pathetically amateurish rap about AIDS a would-be music promoter lays down for the family's uncomprehending patriarch. But the subplot-laden script is too calculated and melodramatic, and the mannered video effects (frames within frames, color mixed with black and white) work against the documentary feel and the actors' raw sincerity. Gene Siskel Film Center, 164 N. State, Saturday, July 20, 4:00 (Singing), 6:00 (Stroke), and 8:15 (Scheme C6); Monday, July 22, 6:15 (Singing); and Wednesday, July 24, 6:15 (Stroke) and 8:15 (Scheme C6); 312-846-2800.