Nag and Nagaina are the deadly black cobras who live near the home where Rikki-Tikki-Tavi lives in Rudyard Kipling's children's classic of the same name. Both of the cobras hunt and kill just about anything they can, and the new English family who inhabit the big bungalow in Segowlee cantonment is high on their list. Nag, the male, is fully five feet long, and all the small animals in the area fear the two cobras. That is, except Rikki.
Rikki learns from Chuchundra the muskrat that
"Those who kill snakes get killed by snakes," said Chuchundra, more sorrowfully than ever. "And how am I to be sure that Nag won't mistake me for you some dark night?"
"My cousin Chua, the rat, told me -- " said Chuchundra, and then he stopped.
"Told you what?"
"H'sh! Nag is everywhere, Rikki-tikki. You should have talked to Chua in the garden."
Chuchundra tells Rikki that he is afraid to run out into the middle of the room for fear of being killed by the cobras. Darzee, the tailor-bird, lost one of her babies to Nag when it fell from the nest. Later, Rikki overhears the cobras planning their next move.
"When the house is emptied of people," said Nagaina to her husband, "he will have to go away, and then the garden will be our own again.
... (Said Nag) "I will kill the big man and his wife, and the child if I can, and come away quietly Then the bungalow will be empty, and Rikki-tikki will go."
But Rikki catches Nag by surprise and hangs on for dear life until the Englishman kills the cobra with his shotgun. After a night of nursing his wounds, Rikki was ready to take on Nagaina as well.