During the course of APO's first mission, to bring down a terrorist and assassin-for-hire, she learns the man was actually hired to kill her - by Irina. Jack subsequently killed Irina to protect his daughter. Meanwhile, Sydney rekindles her romance with Vaughn. Later, it is revealed that Irina is not actually dead - Jack killed a genetic double in an elaborate deception orchestrated by Irina's evil sister, Elena, who recruits Sloane in activating a huge Mueller device invented by Rambaldi, which has the potential to destroy the world. Irina is rescued from Elena's clutches and reunited with her family - including Nadia, who she hasn't seen for years - and together they fly to Russia to stop Elena's plans.