Plot summary
Ari Tasarov turns himself into Division, revealing to having split off from Amanda after she incidentally got international authorities after him. He believes that Amanda has gone too far and is aiding a terrorist group, called the Crimson Resistance, to perform random terrorist attacks and blame them on Division. Ari is willing to help Division stop her in exchange for $50 million. Following a grande attack in Pittsburgh, and a drive-by shooting in Romeo, Michigan, believing Ari is stalling, Nikita resolves to torture the information out of him, until she realizes that Ari intends to use the money to help his son, Stefan, while Ari himself accepts whatever fate awaits him.
Ari eventually reveals that the terrorist Amanda is helping is Saalim Azar (Piter Marek). After Alex and Owen prevent the third attack, Amanda executes Saalim. Division is able to find Saalim's location and delete everything that Amanda used to frame Division for arming him. Amanda decides to go after Stefan.
Credits
Adapted from Wikipedia contributors, Nikita season 3. HTML formatting and reference markers removed.