There stood a massive tree by the riverbank. A very large flock of herons lived on that tree.
Within a hollow of that very tree lived a black cobra. Whenever the eggs hatched and the chicks grew old enough to venture away from their parents, the cobra would devour them. In this manner, for years, the black cobra had been preying upon the heron chicks.
Yet, the herons showed no inclination to leave the place, for the river there teemed with turtles.
The herons were particularly fond of the turtles' tender meat.
This time, as the cobra was about to snatch a chick, the father heron spotted him.
The heron realized that the cobra must have been devouring his previous offspring as well.
He was overcome with grief.
A turtle, seeing him shedding tears, asked, "Uncle, why are you weeping?"
In moments of sorrow, a creature tends to pour out its woes to anyone who will listen.
Recounting the story of the cobra and his deceased children, the heron said, "I wish to exact revenge upon him."
The turtle thought to himself, "Aha! So this is the sorrow over which Uncle is weeping.
Yet, when *he* devours *our* children, it never crosses his mind how much grief *we* must endure. If you wish to take revenge on the snake, then surely *we* would wish to take revenge on *you*!"
The heron had committed a grave error by confiding his troubles to his enemy.
The cunning turtle had already devised a plan to kill two birds with one stone. He spoke up, "Uncle! I can suggest an excellent method for you to exact your revenge."
In an impatient tone, the heron asked, "Tell me quickly—what is this method? I shall remain indebted to you for the rest of my life." The turtle smiled inwardly and began to explain the plan: "A short distance from here lies a mongoose's burrow.
The mongoose is a mortal enemy of the snake. Furthermore, mongooses are extremely fond of fish." "Catch some small fish and lay a trail of them leading from the mongoose's burrow all the way to the snake's hollow tree trunk.
The mongoose will follow the trail, eating the fish as he goes, until he reaches the snake and finishes him off." The heron replied, "Just show me that mongoose's burrow."
The tortoise showed the heron the mongoose's burrow.
The heron did exactly as the tortoise had instructed.
Sure enough, the mongoose followed the trail of fish and reached the hollow tree trunk.
Upon seeing the mongoose, the cobra hissed menacingly.
After a brief struggle, the mongoose tore the snake to shreds.
The heron leaped for joy. The tortoise, however, said to himself, "This is merely the beginning, you foolish heron. Now my vengeance truly begins, and every single one of you herons shall be destroyed."
The tortoise's prediction proved correct. After killing the cobra, the mongoose did not leave the area.
He looked around and saw herons everywhere—a delicious food supply that would last him for months. The mongoose took up residence in the very same hollow tree trunk where the cobra had lived, and every day, he began to prey upon one of the herons. In this manner, one by one, all the herons were killed.