Sometime later Zack, now promoted to 1st class SOLDIER, travels with Sephiroth and Cloud to investigate a mako reactor near Nibelheim. Sephiroth discovers he himself was an experiment, implanted with cells of the extraterrestrial Jenova. In his anger, Sephiroth sets Nibelheim's town ablaze. Zack attempts to defeat Sephiroth but fails, but Cloud arrives and despite being impaled by Sephiroth's sword, is able to throw Sephiroth into the Lifestream. Zack and Cloud fall unconscious. Zack awakes to find he and Cloud part of Dr. Hojo's experiments on Jenova cells and Mako exposure; while Zack is unaffected by the Jenova cells, thanks to the genetic modifications already present in him thanks to SOLDIER, Cloud has reacted badly to the introduction of Jenova cells into his body and is unable to move on his own. Zack helps Cloud to escape and they quickly become high priority targets for the Shinra forces. Zack encounters Cissnei during their escape, but she does not capture them, instead allowing them use of a Turk motorcycle. While fleeing, Genesis intercepts Zack and Cloud, and makes one of his clones eat a lock of Zack's hair. When this causes the mutation to go awry, Genesis flies away. Zack, realizing that Genesis is trying to stabilize his mutation, vows to defeat Genesis before being captured again.