How does Ricky Tikki tabby protect Teddy's father?

Rikki-Tikki-Tavi protects Teddy's father by bravely confronting and ultimately killing the cobra Nag, who poses a lethal threat to the family. After discovering Nag's plan to attack, Rikki devises a strategy to outsmart the snake, luring him into a confrontation. His quick reflexes and determination ensure the safety of Teddy's father, allowing the family to live peacefully in their garden once again.