Season synopsis
Contains spoilers for this season and earlier seasons.
Sydney leaves the CIA and joins Authorized Personnel Only, or APO, a black-ops team led by Arvin Sloane and staffed by Jack, Vaughn, Dixon, Marshall and Nadia. The arrangement puts Sydney back in the field with her former colleagues while forcing her to work under the man whose past crimes still threaten her family. When Sydney finds evidence concerning Jack’s role in her mother’s supposed death, the discovery strains their relationship. APO’s early cases range from a stolen information system to a terrorist training camp and a chemical threat.
The team’s missions bring old adversaries back into their orbit, including Anna Espinosa and Sark, while Nadia’s history repeatedly complicates her place inside APO. Jack’s records about Vaughn’s father lead Sydney and Vaughn into a separate investigation of Vaughn’s identity and family past. Sloane’s conduct also comes under suspicion when Dixon believes he is using APO to steal the Blackwell Index. A double of Sloane emerges in a later case, and the team must work out how the impostor connects to the Rambaldi materials before the real Sloane can act.
Before the final operation, Vaughn proposes aboard the plane to Sovogda; Sydney accepts as the team parachutes toward Elena’s Mueller device, which has driven the city into a violent frenzy. Nadia becomes infected and turns against Sydney, so Sloane shoots her to stop the attack. Nadia survives, stable but sedated, as the team destroys the device. Irina is released, and she and Jack part after facing their past. Driving toward Santa Barbara, Sydney suggests eloping. Vaughn says he must first tell her the truth: Michael Vaughn is not his real name. A vehicle strikes their car before he can explain, leaving his fate uncertain.