Orochimaru's Hideout Discovered (発見 大蛇丸のアジト, Hakken - Orochimaru no Ajito) is episode 91 of the Naruto: Shippūden anime.
Synopsis
Guren takes twenty-one survivors from the hideout and leaves to meet with Orochimaru. Team Kurenai and Kakashi arrive at Orochimaru's hideout, only to discover that it has already been abandoned. Guren uses her Crystal Release technique to kill sixteen of her charges when they try to revolt. The other five align themselves with Guren. Meanwhile, Naruto tries to find a ranged attack to use, and Jiraiya wants to train him in synchronising techniques. Unfortunately, Naruto does not get along well with Gamariki, with whom he is supposed to synchronise.