After selling the executioner some five-strand rope needed for the hanging, Sykes sells a bag of dust to the condemned man's father, collecting ordinary dirt from the ground and insisting that it is magic dust that will spread good will throughout the crowd and make them feel love and sympathy for Luis.
He hears the trapdoor drop behind him and turns to see that the fresh and sturdy rope has snapped above the noose, and Luis is unharmed.
When asked if another hanging attempt should be made, the girl's parents decide that it should not, that Luis has suffered enough and maybe they have had a sign from God.
As father and son walk home, Sykes rechecks the rope which appears to be in perfect condition.
And if there's any moral to it at all, let's say that in any quest for magic, in any search for sorcery, witchery, legerdemain, first check the human heart.