This is the Lost Episode of ALIAS.
Sydney returns from maternity leave after giving birth to baby Jack. She learns that her mother is indeed alive and that after their last encounter when Sydney gave birth to Isabelle, her mother knew that the CIA would be after her. So she created another clone, which battled Sydney in the roof in the Season 5 finale. She also learns that she is working with Sark, and they've found a way to cure Sloane. Sydney and the team must beat Sark and Irina. Sark and Irina cure Sloane and break Peyton out of jail. When Peyton, Sark, and Irina are dead, Sydney discovers the only thing that can reverse Sloane's immortality - the blood of the Chosen one.
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