Rikki-tikki wakes the next morning and continues his exploration of the bungalow before venturing outside into the family’s garden. In the garden, the mongoose meets two tailorbirds, the carefree Darzee and his more sensible wife. The two birds tell Rikki-tikki that they are sad because one of their babies fell out of their nest and was eaten by someone named Nag. Rikki-tikki explains that he is a stranger to their garden and therefore does not know who Nag is, but the two birds cower in their nest without offering an explanation. Rikki-tikki is then immediately set upon by Nag, a vicious cobra who, along with his wife Nagaina, hold dominion over the bungalow’s garden. The two cobras resent the British family that owns the estate, and they are enraged that they have welcomed a mongoose into their home because mongooses are known to kill snakes. Convinced that Rikki-tikki will harm their eggs, Nag and Nagaina try to kill the mongoose first. Nag pretends to converse with Rikki-tikki so that Nagaina can sneak up behind the mongoose and kill him. Their plan is thwarted when Darzee yells for Rikki-tikki to look behind him. Rikki-tikki is briefly frightened, but he soon summons his courage and remembers that it is a mongoose’s “business” to fight and eat snakes. He keeps a level head and fights with the two cobras until they reluctantly admit defeat and retreat to their hole.  

Teddy comes running outside to play with Rikki-tikki shortly after his victory against the cobras. However, just as Teddy is about to reach him, the mongoose hears a tiny voice cry out, “Be careful. I am death!” Rikki-tikki locates the voice and realizes that a dusty-brown and poisonous snakeling named Karait is heading toward the young boy. Rikki-tikki , unaware that Karait is even more dangerous than the cobras because he is much faster, advances on the snakeling. Teddy cries out and his parents watch as Rikki-tikki fights and kills Karait. Teddy’s father then beats the dead Karait, much to Rikki-tikki’s bemusement. Teddy’s parents are overjoyed that their new visitor has saved their son and Alice thanks him profusely. The family then welcomes him back into their home. 

That evening, on his nightly walk after Teddy falls asleep, Rikki-tikki meets Chuchundra, a cowardly musk-rat who lives in the bungalow as well. Chuchundra alerts Rikki-tikki that Nag and Nagaina have entered the bungalow. Rikki-tikki then creeps along the estate, looking for his adversaries. He soon overhears Nag and Nagaina plotting to kill the entire family so that they can take over the bungalow for their hatchlings. The two snakes split up and Nag hides in the family’s bathroom so that he can surprise and kill his victims in the morning. However, Rikki-tikki manages to sneak up on Nag and attack from above, fatally sinking his teeth into Nag’s hood. The commotion wakes Teddy’s father, who storms in and shoots Nag with a shotgun. Alice and her husband are pleased that Rikki-tikki-tavi has protected their family for the second time that day, and the exhausted mongoose drags himself to Teddy’s room to rest.