Best known for Low Life, his book-length portrait of Manhattan’s underclass in the early 20th century, Luc Sante is the Belgian-born polymath who’s spent the past 30 years writing about social history and art. This week at Northwest Film Forum, Sante gives a live performance that explores his twin obsessions onscreen, mapping the underbelly of Paris via clips from such films as Maurice Cam’s Métropolitain and Jules Dassin’s Rififi and providing running commentary throughout. (Northwest Film Forum, 1515 12th Ave,, 8 pm, $15, April 18–20)