Rikki-tikki, a mongoose, is swept from his burrow by a flood and is rescued by a young boy, Teddy. The family decides to adopt Rikki-tikki.
The safety of the garden is threatened by the two cobras, Nag and Nagaina. Rikki-tikki decides he will kill the cobras, but first, he kills another deadly snake. It is his first kill, and man and his wife hail him as a hero.
Nag falls asleep in the bathroom while he waits to attack the humans. Rikki-tikki wins a terrible battle against the cobra. The man shoots Nag in half, and throws the snake on the trash pile.
Darzee’s wife fakes a broken wing to distract the cobra. Nagaina leaves her nest of nearly-hatched eggs and begins to chase the bird. Rikki-tikki kills the unhatched cobras and Darzee's wife calls out a warning. Thinking the man killed her husband, Nagaina corners the entire family on the veranda.
Rikki-tikki taunts Nagaina with one last egg. She is frantic and begs for her baby back. With the snake occupied, the family escapes. Rikki-tikki knows that if he does not kill Nagaina, neither the family, nor the garden animals will ever be safe. He attacks and chases her into her underground den. Rikki-tikki emerges victorious, announcing that Nagaina will not return.
The family and animals rejoice. Rikki-tikki eats a huge celebration meal with the family, and settles down as the proud protector of his human family and garden animal friends.