Rudyard Kipling's "Rickki Tikki-Tavi" is a story about a mongoose, his friends, and a little boy. The opening lines of the story tells us the plot:
This is the story of the great war that Rikki-tikki-tavi fought single-handed, through the bath-rooms of the big bungalow in Segowlee cantonment. Darzee, the tailor-bird, helped him, and Chuchundra, the musk-rat, who never comes out into the middle of the floor, but always creeps round by the wall, gave him advice; but Rikki-tikki did the real fighting.
Rickki Tikki-Tavi is a spunky mongoose who, when we first meet him, is unconscious, washed up near a bungalow by a flood. The young boy who lives there discovers the creature and takes him in. Rickki-Tikki-Tavi soon becomes a beloved family pet.
He meets Darzee and his wife as they are mourning the loss of one of their babies that was eaten by Nag, the evil rattlesnake who also lives in this garden. As they talk, Nag senses that he must take action quickly against Rickki-Tikki-Tavi, as he knows that a mongoose is a rattlesnake's worst enemy.
Nag's wife, Nagaina, attacks from behind, but the mongoose is able to elude the strike because of Darzee's warning. This is Rickki-Tikki-Tavi's first experience with snakes, and his escape has given him a false confidence in his ability to defeat them. As Teddy (the boy) runs to him, Rickki-Tikki-Tavi sees a small but poisonous snake and the mongoose's eyes turn red--the sign every mongoose gives before he is about to attack. Rickki-Tikki-Tavi kills the snake and receives grateful thanks from Teddy's parents for saving their son's life.
Later that night, Rickki-Tikki-Tavi is keeping guard on the house and meets a timid little muskrat named Chuchundra who reveals a plot that he has discovered. The mongoose keeps his ears open and overhears Nag and Nagaina plotting to kill the boy and his family in hopes of getting rid of Rickki-Tikki-Tavi. He also learns a very important piece of information: Nag and his wife have a nest of eggs.
Nagaina leaves, but Nag waits, coiled up in the bathroom until he has a chance to strike. Rickki-Tikki-Tavi is very afraid, but he knows what he has to do. He waits until Nag is sleeping, grabs the snake from behind, and eventually manages to kill Nag. Teddy's father hears all the ruckus and runs in with his shotgun, shooting the already dead snake.
Rickki-Tikki-Tavi knows the worst is ahead, for now he has to deal with Nagaina. He asks Darzee for help, and Darzee tells the mongoose that Nagaina's eggs are hidden in a nest in the melon patch, though the bird does not understand why that piece of information is significant. While Darzee is a little foolish about these things, his wife knows perfectly well that snake eggs will eventually become actual snakes that will threaten all of them in this garden.
Darzee's wife fakes an injury to her wing in order to distract Nagaina (at some risk to herself, of course), allowing Rickki-Tikki-Tavi enough time to go destroy her eggs. Next the angry Nagaina attempts to take her revenge on Teddy's father for killing Nag. Darzee's wife manages to warn Rickki-Tikki-Tavi about the plan, and the mongoose arrives for a showdown on the terrace just as Nagaina is poised to strike.
Rickki-Tikki-Tavi has the last snake egg and distracts her with that, taking responsibility for killing Nag. A grand battle ensues, but it takes place underground in Nagaina's lair. The mongoose wins, of course, and Rickki-Tikki-Tavi becomes a permanent part of the family.