As David Fincher demonstrated in his criminally underrated Zodiac, something weird was happening in San Francisco in the 1970s. A truly terrifying serial killer was on the loose; social mores were crumbling in a haze of drugs, sex, and protests; and gay rights were finally entering the mainstream. Salon founder David Talbot’s new book, Season of the Witch, argues that San Francisco was the cradle of the modern age and that all of our important progressive causes—from gay marriage to Occupy, and all the other beliefs that conservatives call “San Francisco values”—were born then and there. (Town Hall, 1119 Eighth Ave,, 7:30 pm, $5)