When local outcast Manuel Avila is lynched for stealing a calf, his father Juan (Peter Mamakos) swears revenge. Together with his other sons, Quito (Armand Alzamora) and Carlos (John A. Alonzo), he takes the local saloon hostage, vowing to kill one person every ten minutes until Sheriff Cal (House Peters Jr.) shows up. Cal refuses, believing that violence on his part will only make the situation worse, even though his son Johnny (Gary Gray) is one of the hostages.
Terror at Black Falls contains examples of:
- Character Narrator: Sheriff Cal narrates throughout the movie.
- Cruel Mercy: Juan plans to kill Johnny last so he can watch everyone else die.
- Death by Childbirth: Manuel's mother died giving birth to him. Juan accepts this, saying it's God's way for parents to die and leave their children to take their place. He is enraged that Manuel died without children.
- Died in Your Arms Tonight: Johnny shoots Quito, who dies in Juan's arms.
- Face Death with Dignity: As he's led up to be hanged, Manuel is surprisingly calm, refusing to cry or show fear. Once he actually starts hanging, though, he screams, "PAPA! PAPA!"
- Grievous Bottley Harm: At one point, Carlos tries to beat a hostage with a rifle. Juan stops him by throwing a bottle, which smashes against the back of Carlos's head.
- I Need a Freaking Drink: Juan's vow of revenge drives the nervous, stressed-out townspeople to drink, even the ones who normally stay sober. This means that the saloon is quite crowded when Juan arrives.
- Spiteful Spit: Billy (King Moody), one of the saloon's patrons, spits at Juan but falls several feet short. This starts a confrontation that ends with Billy dead.
- Vigilante Execution: Sheriff Cal and the Avilas both rush to stop Manuel from being hanged, but they are too late. Enraged, Juan tries to shoot Cal, who shoots him in the hand. Juan's hand later has to be amputated, which gives him another reason to want revenge.
- Zipping Up the Bodybag: When Johnny kills Quito, Juan lays his body on the bar and pulls a blanket over it.
