Teddy shouted to the house: "Oh, look here! Our mongoose is killing a snake”; and Rikki-tikki heard a scream from Teddy's mother. His father ran out with a stick, but by the time he came up, Karait had lunged out once too far, and Rikki-tikki had sprung, jumped on the snake's back, dropped his head far between his fore-legs, bitten as high up the back as he could get hold, and rolled away. That bite paralysed Karait, and Rikki-tikki was just going to eat him up from the tail, after the custom of his family at dinner, when he remembered that a full meal makes a slow mongoose, and if he wanted all his strength and quickness ready, he must keep himself thin.

Who is the protagonist in this excerpt?