A young woman graduating from college marries a much older man (a professor) because he is rich.

After their marriage they move to South America so he can conduct research.

One of the customs of the tribe that they live with is that they make those accused of wrongdoing drink from a spring that will apparently prove whether or not they are guilty. If you're innocent you are supposed to be fine and if not, you die.

The water is known to be clean but they witness an accused woman die when she is forced to drink it.

The real trouble starts when the tribe's chief accuses the professor's wife of being unfaithful to her husband and asks her to drink the water. 