The plot follows the title character, a German governess hired to look after two unruly boys whose parents have taken a six-week vacation.

By day, Miss Forbes runs the household with oppressive discipline but at night she displays a behavior more troubling than the one shown by the children who resist her authority.

The household is completed with the superstitious indigenous cook and a local young fisherman who serves as the children underwater swimming instructor.

Mrs. Forbes arrives by boat after a long trip and she is immediately instructed by the mother to impose "law and order" in the house and to treat the undisciplined and rude children severely in an attempt to improve their ways.

Spying on her at night, the brothers discover that she walks around the house drinking alcohol, eating sweets, and reading loud strange passages in German.

From her arrival, Mrs. Forbes is smitten with Aquiles, the hunky young scuba instructor who spends a great deal of time around the house playing with the children and at sea with them while wearing very little.

All along since Miss Forbes forced the two boys to eat moray, the same fish that they were terrified of when it was nailed to the door of the house, the children have planned to kill her poisoning her tequila.

They see her lying dead surrounded by blood with multiple stabs and cuts instead of the poisoned tequila the boys planned her to drink.

The Summer of Miss Forbes was one part of a series of six films, co-produced by Spanish TV and born out of Colombian novelist Gabriel García Márquez's interest in cinema.

While the original short story takes the point of view of the narrator, one of the boys, the film centers on the governess and the apparent duality of her personality.

The character of Aquiles, the handsome fisherman, was further developed and took an important role in the film as the love interest of Mrs. Forbes.