The Pearsons come together to celebrate Kate and Toby's wedding. Wedding planners Kevin and Randall struggle to pull off the big day. Kate is flooded with memories of Jack. Deja struggles to adjust to her new living situation.
Sydney finds herself face-to-face with her mother, whose intentions for her daughter are made chillingly clear. Meanwhile Sydney continues her search for Vaughn, not knowing if he is dead or alive after being swept away by a wall of water in Taipei. Will's life is forever changed when he learns the truth about SD-6 and Sydney's life as a double agent. Dixon must decide whether or not to inform Sloane of Sydney's suspicious activities.
Sydney, Jack and Irina must put aside their differences and go undercover as a loving family in order to seize six nuclear warheads from an unfriendly nation. Meanwhile, Sloane announces to a suspicious staff that Mr. Sark will be working with SD-6, and later he is contacted by an unknown group claiming that Emily is still alive.
Lindsay's parents forbid her from hanging out with Kim, as they see her as a bad influence. Bill grows tired of being picked last for teams for baseball in P.E. class, and not being allowed to really participate.
Sydney begins to question Will's identity when he's arrested for espionage, under suspicion of being a double. Meanwhile Sark and Irina plot to recover the Rambaldi heart, and Sloane makes Jack a business proposal.
It's the Big Three's 37th birthdays. Randall and Beth debate a big life change, Kate takes the first step in pursuing a new passion, and Kevin balances the demands of his career and relationship. Meanwhile, Jack and Rebecca deal with the fallout of their big fight.
Sydney's life is placed in mortal danger when Sloane is informed by his superior that she is the SD-6 mole. Meanwhile, Dixon's life hangs in the balance after he is shot on a mission, and Will realizes that his discovery of Kate Jones' pin could uncover some unexpected information.
Will's life is about to change as he is sent to find the person responsible for leaking information to him about SD-6. Meanwhile, Sloane finds himself on the cusp of finally tracking down Khasinau when SD-6 captures "The Man's" right-hand man, Mr. Sark. Dixon becomes suspicious of Sydney's activities.
Sydney gets shocking info on her dad's role in Danny's murder and takes on a countermission against the SD-6 to bring down an arms dealer linked to a missing nuclear weapon. Meanwhile, Will begins to grow suspicious of his friend's secret life; and Vaughn is taken off Syd's case after his mishap puts the entire world in danger.
Sydney tries to piece together the last two years of her life and discovers the fates of her friends and family. She confronts Vaughn about his marriage and learns the shocking fates of Jack and Sloane. Meanwhile, she is granted temporary CIA clearance on a case that may help her regain her memory.
After making a shocking discovery in the desert, Sydney agrees to submit to an experimental procedure conducted by an eccentric doctor, designed to retrieve her lost memories. But while Jack and Vaughn look on, Sydney's mind proves surprisingly resistant to letting her remember her missing time -- and the process of recovering it could end up killing her. Meanwhile, Lauren makes a great sacrifice in order to make her alibi believable to Lindsey after breaking Sydney out of NSC custody, and Sloane finds himself boxed in by an unlikely enemy -- one who wants to see Sydney Bristow eliminated permanently
After learning that the man she has known as Michael Vaughn is under investigation and suspected of being a double agent, Sydney begins to question whether their business and personal relationship over the years had all been a lie.
"The Train" is the best rated episode directed by Ken Olin. It scored 9.5/10 based on 4 votes. It was written by N/A. It aired on 5/17/2022 and is rated 0.2 points higher than their second-best episode, "Katoby".