"The Bewildering Forest" (迷いの森, Mayoi no Mori) is episode 210 of the original Naruto anime.
The boat that Naruto's group was on washed over a waterfall, allowing Naruto, Gantetsu and Todoroki to escape into the forest. Naruto learned from Gantetsu that the forest was the Ninja Dropout hideout, and that only a Ninja Dropout like him could find the way through. Naruto's group defeated one of the Ninja Dropout members, who attacked with a large claw-like machine. Sakura and Lee encountered some orphans who were taking refuge in the forest. It was then revealed that Todoroki intended to kill Gantetsu to avenge his family, and would go so far as to kill Naruto to eliminate a witness to his crime.