When a summer flood washes a young mongoose out of its burrow, an English boy named Teddy finds him and brings him to his parents. They warm and dry the mongoose, who revives and then climbs up onto the young boy’s collar. The mongoose is called Rikki-tikki-tavi because of the chittering sounds he makes, and he is a brave and curious animal. The English family feeds him and then he goes to explore the house. By night, he sleeps beside Teddy, although Teddy’s mother is worried that Rikki-tikki-tavi will bite the child. Teddy’s father reassures her that the mongoose will actually keep Teddy safe from snakes.

The next day, Rikki-tikki-tavi goes to explore the garden of the bungalow, which is in an area of India called Segowlee where many military families live. In the garden, Rikki-tikki-tavi hears Darzee the tailor-bird and his wife crying because one of their babies fell out of the nest and was eaten by the cobra, Nag. Nag appears and claims that the god Brahm put a mark upon his hood in thanks for keeping the sun off of him while he slept. Rikki-tikki-tavi is frightened at first, but since a mongoose’s natural instinct is to eat snakes, he is not afraid for long.