Conservation filmmaker Ben Masters realizes the urgency of documenting the last remaining wilderness in Texas as the threat of new border wall construction looms ahead. Masters recruits NatGeo Explorer Filipe DeAndrade, ornithologist Heather Mackey, river guide Austin Alvarado, and conservationist Jay Kleberg to join him on the two-and-a-half-month journey down 1,200 miles of the U.S.-Mexico border.