"The Top-Secret Mission…!!" (極秘任務…!!, Gokuhi Ninmu…!!) is chapter 298 of the original Naruto manga.
Naruto examines the area and is confused by the damage, unaware that he is responsible for everything. They come across the location of Sai, meeting with Orochimaru and find a number of Sai's belongings, including his picture book, strewn around the area. Yamato, his wood clone having seen it firsthand, informs them that Sai has joined up with Orochimaru and that the wood clone is following them back to their base. They assume that Sai is working with Orochimaru on Danzō's orders and intend to find him to determine why, but must wait for Naruto to rest, use of the Nine-Tailed Demon Fox negatively impacting his body. Meanwhile, Yamato's wood clone comes across Sai hanging from a tree.