Set in rural Southern Mexico, an American cattle rancher (Guy Madison) finds himself the rival of a native Mexican rancher (Eduardo Noriega) in both business and in love. The woman (Patricia Medina) in contention is conflicted in her loyalties and emotions. Meanwhile, cattle and people are disappearing around the swamps below Hollow Mountain. Despite the title, the film focuses on the tense triangle of the three protagonists as well as a subplot involving a little boy (Mario Navarro) and his heavy drinking father (Pascual Garcia Pena). The beast doesn't arrive until the movie's final 20 minutes. An American-Mexican co-production with two directors, Edward Nassour and Ismael Rodriguez, the film was the brain child of stop motion animation pioneer Willis H. O'Brien (KING KONG). It's a rather slow moving western and disappointing given the limited time of the title creature. To the film's credit, I liked how Medina's heroine was feisty and instead of screaming like a ninny when confronted with the beast, she fights back. On the other hand, when Madison first spots the beast instead of being amazed, he has the look of "Oh, it's just another dinosaur". With Carlos Rivas (THE KING AND I) and Julio Villarreal.