Vagabond Lassie pulls border-jumping Roberto from the muddy bank of the Rio Grande near Texas border town Del Rio. Lassie leads a young couple back to the exhausted boy in time to thwart a scruffy hippie stealing the boy's shoes. They feed and hear his tale: Mom dead, Dad U.S. traveling salesman; boy left in Saltillo, Mexico with aunt who does not love him. He came seeking Dad. Vindictive hippie calls the cops on the "wetback." Lassie and boy run off. Morning, cops chase, Lassie finds Dad at newsstand, reunion, boy cleared with cops, Lassie returns to vagabond freedom, satisfied she helped.