Wild stallion Cloud, whose herd was recently mustered.
Its screening comes just a month after the controversial muster of Cloud and the other wild horses living in the Pryor Mountains, on the Montana-Wyoming border.
While Cloud and some of his herd were released back into the wild, a total of 57 horses were held back and sold at auction.
The Cloud Foundation, a wild horse advocacy group which condemned the muster, raised concerns over the need for the roundup and argued that the famous herd would be left genetically non-viable and unable to sustain itself in the future.
The foundation's volunteer executive director is Ginger Kathrens, an award-winning documentary film-maker who filmed footage of Cloud on the day he was born.
The third documentary in the series, entitled "Cloud: Challenge of the Stallions", screened across the US on Sunday evening on PBS stations.
Several members of Cloud's herd were sold at auction after the muster.
The documentary shows Cloud fighting to win new mares, the birth of surprising foals, lethal predators and a government bait-trapping operation that endangers Cloud's family.
"I hope the new show underscores just how complex wild horse society is," Kathrens says.
"And not just complex but unpredictable. In my wildest dreams I never imagined a story this dramatic."
The first two shows, "Cloud: Wild Stallion of the Rockies", produced in 2001, and "Cloud's Legacy: The Wild Stallion Returns", from 2003, chronicle the first eight years of Cloud's life. It all began when a newborn wild horse foal tottered out of the forest right in front of Kathrens' camera. She named the pale colt Cloud and has followed him through the seasons, creating the three documentaries.