Mark, Jasper and Lily are high school friends now in their early twenties. Mark is gay, living with Lily (his high school girlfriend), while Jasper is straight and soon to be married. A cynical and bitter trio barely connected by their past friendship, they reunite for the annual public Halloween celebration in San Francisco's Castro district. When the huge crowds of costumed revelers fail to entertain them, they begin a quest to find an elusive acquaintance who might provide them with some ecstasy.

This quest is interwoven with an abstracted remembrance of a high school camping trip the three friends took to the Lost Coast, a lush wilderness in northern California, during which Mark and Jasper were involved in a sexual relationship that Mark never got over, and Jasper never acknowledged.

Over the course of their evening in San Francisco the three are forced to confront this past, which has held them all in suspended animation. The Lost Coast explores the complexities of sexuality, repression, and isolation, with a quiet, measured style.
The film was shot almost entirely outdoors in San Francisco and Marin County, California in March of 2006, the rainiest March in the Bay Area's history (it rained 29 out of 31 days). The mud, wet and cold were more than made up for by the overcast light, which provided a perfect visual tone to the film. The first day of shooting was October 31, 2005, when the cast and a three person crew braved the two hundred thousand people crowding San Francisco's Castro district for the public celebration of Halloween, a filming feat that would have been difficult if not impossible for a big-budget film. The Lost Coast is a kind of portrait of late-night San Francisco on Halloween, as the characters move from the Mission to the Castro, through Golden Gate Park and the Sunset District, finally to the beach overlooking the Pacific Ocean.