The Enemy: Ninja Dropouts

is episode 209 of the original Naruto anime.

Synopsis
Naruto, Sakura and Lee are hired to escort a "Ninja Dropout"- a criminal ninja- named Gantetsu to prison, and guard him against his comrades, who may be trying to free him. They learn that Todoroki, the captain of the guard, has a personal vendetta against Gantetsu for what happened to his parents and [Akio|younger brother]]. During an attack by one of the Ninja Dropouts, Naruto, Todoroki and Gantetsu are separated from Sakura, Lee and the guards.