Every year more than thirty million people cross between San Diego and Tijuana through the San Ysidro Port of Entry, the busiest land border in the world, and the film follows what happens to the people pushed out the other direction. About 40 percent of Mexican nationals deported from the US are sent back through Tijuana, and many end up in El Bordo, a shantytown built inside the concrete channel where the Tijuana River used to run. The film traces how the crossing itself got harder to reach: Operation Gatekeeper in 1994 expanded the border wall and added checkpoints, and drone patrols have since made this stretch one of the most fortified in the Americas, pushing crossers toward routes like the Sonoran Desert, where hundreds die each year. What remains at San Ysidro is the aftermath, a riverbed community of people who tried to go north and got sent back with nowhere else to go.