Season synopsis
Contains spoilers for this season and earlier seasons.
Sydney wakes in Hong Kong after two years away and discovers that Vaughn has married Lauren Reed. The CIA doubts her account and detains her while Jack and Sloane work to bring her back. Kendall eventually explains the missing years: the Covenant staged her death and tried to condition her as assassin Julia Thorne. Protected by her childhood Project Christmas training, Sydney pretended to cooperate and secretly pursued a Rambaldi cube with Andrian Lazarey. After securing it, she deliberately erased her memories so she could not reveal its location; Kendall had promised not to tell her.
Back at the CIA, Sydney works with Jack, Vaughn, Dixon and Sloane to stop the Covenant while trying to rebuild a life interrupted by the missing years. Vaughn’s marriage strains under the truth about Sydney’s disappearance, and Lauren is exposed as a Covenant operative working with Julian Sark. The team’s missions lead them toward a Rambaldi text about the Passenger; Sydney’s half-sister Nadia is identified as that figure and becomes entangled in Sloane’s pursuit of the prophecy. Sloane’s apparent reform remains difficult for Jack and Sydney to trust.
Sydney and Vaughn’s final pursuit brings them into conflict with Lauren and Sark as they try to stop the Covenant’s Rambaldi plan. Lauren escapes custody and attacks Sydney, but Vaughn reaches them and shoots her. Nadia leaves with Sloane after telling him she changed the equation in the Rambaldi papers. Following Lauren’s last clue, Sydney opens a vault in Wittenberg and finds secret CIA records carrying her name and identifying Jack as project manager. He appears as she reads, leaving his role another unanswered question.