Allen Ross, who cofounded Chicago Filmmakers in the early 1970s, vanished mysteriously in 1995, two years after he surprised his friends by suddenly marrying alleged cult leader Linda Greene and leaving Chicago. German filmmaker Christian Bauer says that for both of them filmmaking was a "way of understanding the world," and his 2001 documentary tries to unravel the story behind Ross's disappearance. Documentaries about failed quests are commonplace, but Bauer encircles his subject with a poetic structure based on gaps and disjunctions, presences and absences (Allen's camera is found in storage, but where is he?). Ross emerges as a gentle spirit, loved by many, who for reasons unknown apparently got in over his head with Greene and an ex-husband, each of whom accuses the other of putting a bullet in Ross's skull. Bauer includes Greene's loopy (and creepy) writings, faxes, and phone messages: her published protocol for dealing with vampires included removing their genitals--which was done to Ross, whose remains were discovered in a Wyoming basement. No arrests have been made. Bauer will attend the screenings on Friday, March 1, and at 9 AM on Monday, March 4, he'll hold a press conference at Chicago Filmmakers, 5243 N. Clark, to screen additional footage of an interview with Greene. Missing Allen will be shown in 35-millimeter, transferred from video. 91 min. Gene Siskel Film Center, 164 N. State, Friday, March 1, 6:15 and 8:15; Saturday, March 2, 4:15, 6:15, and 8:15; Sunday, March 3, 4:15 and 6:15; Monday through Wednesday, March 4 through 6, 6:15 and 8:15; and Thursday, March 7, 6:15; 312-846-2800.