Narrated by Academy Award-winning screenwriter Dustin Lance Black -- who like Cowan is gay and was raised Mormon -- the 81-minutes film opens with footage of gay couples saying , " I do , " in San Francisco 's City Hall on June 17 , 2008 , the first day gays could legally marry and then chronicles what some say was the most expensive initiative campaign in California 's history through election day and angry postelection protest marches outside Mormon church temples nationwide .