Sydney, a young woman with an uncanny ability to communicate with animals, is on the run from her long-lost mother, Irina Derevko. The two have not seen each other in years, but Sydney has been sent back to Los Angeles by her father to find out what happened to her mother. As Sydney searches for Vaughn, who she believes is still alive after being swept away by a wall of water in Taipei, she discovers that he is actually working for the CIA. Vaughn had been trying to get information about SD-6, a group of people responsible for sabotaging nuclear reactors around the world. Meanwhile, Will, a fellow agent working alongside Sydney, learns the truth about SD-6 and the role Sydney played as a double agent. He becomes furious at her actions and vows to expose her to the authorities. Dixon, Sydney's handler, must decide whether or not to tell Sloane about Sydney's suspicious activities. But Jack intervenes and covers for Sydney, who later finds Vaughn who helps her try to track down her mother Irina who's searing for a Rimbaldi artifact called "the Bible." Irina, who Sydney had never met before, is now determined to find her daughter and bring her home. She sets off on a dangerous mission to obtain the "bible," which she believes will give her the answers she needs to find Sydney. Meanwhile, Sydney and Vaughn are reunited and begin their search for Irina. They encounter various obstacles along the way, including a group of assassins sent by SD-6 to kill them. In the end, they manage to escape and continue their journey towards Irina. As they near their destination, Sydney and Vaughn discover that Irina has already found the "bible" and is using it to locate Sydney. They race against time to find a way to stop Irina before she can complete her mission. In the end, Sydney and Irina reconnect and share a heartfelt reunion. Sydney learns the truth about her past and the sacrifices her mother made to save her. Together, they embark on a new journey, one where they work together to protect the world from the dangers that lurk beyond its borders.