In the safety of a hotel in Sienna, Sydney remembers her childhood where she assembled building blocks she found lying around. Not realising that this was part of Project Christmas - meant to test people's aptitude for being operatives - Sydney shows her father what she had done. Jack tells her she is a special girl.

Later Sydney reads a report where two missiles were stolen, and assumes Sloane's involvement. Syd concludes that if Sloane had killed all Prophet Five members, he must have all their assets, and would have bought these missiles from someone. Marshal then hacks into the Russian bank network and looks into the phone records. Via satellite, they were able to locate Peyton.

Vaughn, Dixon and Sydney interrogate Peyton, where she reveals that she does not know where the missiles are stored now but she knows that Sloane is targeting two cities with high civilian concentrations. Jack remarks that Sloane is not interested in devastation -he wants to Prophet from the reconstruction. Sydney also finds out that Sloane is in Mongolia.

As Syd was getting ready to fly to Mongolia, Rachel reports that she and Marshall are trying to hack into optical satellites to locate the missiles. They later realise that Sloane had hacked into the network with information uploaded from a contact in Hong Kong. With Dixon interrogating, Peyton reveals who their contact is.

Sloane and Sark go inside the cave in Mongolia. Later, Sloane says that the next step is for him alone to do. Sloane journeys down to a chamber that turns out to be Rambaldi's burial place-and filled with awe, he takes the sphere and puts it on top of Rambaldi's tomb. The Sphere of Life glows and activates Rambaldi's Mueller device with the red hovering ball.

Vaughn, Syd and Jack infiltrate the camp set up outside of Rambaldi's tomb. Syd sneaks into the underground chamber and holds Sloane at gunpoint. Meanwhile, Vaughn and Jack get surrounded by Sark and his men. Syd grabs the Rambaldi sphere and the liquid from the hovering ball drops to the ground. When she was about to destroy it, Sark arrives holding Vaughn and Jack at hostage.

Now having Syd at gunpoint, Sloane urges her to give the sphere back. Sloane turns around and shoots Jack. Syd drops the sphere to go over to Jack and Vaughn takes this opportunity to hit the guards and fight with his captors. Syd shoots Sloane several times and Sloane falls into a pool of liquid that came from Rambaldi's device. He dies and Sark picks up the sphere.
Syd flashes back to when she hands her father one of her first pay checks. When she mentions that she started working for Credit Dauphine, Jack tells her to quit immediately. Confused, Sydney argues that she will do what she wants and what she believes is the best for her.

They carry a severely wounded Jack out the chamber where they attempt to perform first aid. Vaughn reports that Sloane died and Sark must be headed towards their contact in Hong Kong with the Rambaldi sphere. Vaughn adds that it is Irina Derevko.

Later, the team receives a report that while Marshall can access launch protocol, they can't stop the initialising sequence. Jack advises them to go to Hong Kong. When Syd wanted to stay, Jack urges that she is the only one who can stop her mother. He adds that he never wanted this life for Sydney, but Sydney is far too driven and strong to let anyone stop her. Syd tells her father that she loves him and leaves hesitantly.

In Hong Kong, Sark comes to Irina and reports that the missiles are ready. When Irina tells him to target London and Washington D.C., Sark goes to a control room where he commands his men to initiate the countdown.

When Sydney arrives, Irina tells her that power is the only currency -and through Rambaldi, they can live forever. Syd and Irina fight furiously. Meanwhile, Vaughn breaks into the control room where Sark is in and they engage in combat. Vaughn shoots Sark and demands for the code to stop the missile launch. With Marshal's help, the launch is aborted. Meanwhile, in Mongolia, the bullet holes in Sloane heal and he is restored to life. As he starts to walk out the chamber, a wounded Jack stops him.

Jack apologises for not believing in Rambaldi but since Sloane caused Sydney so much pain, he is determined to not let Sloane do it again. When Sloane says he can't be hurt anymore in his immortality, Jack points out that he can keep him in that underground cave with him. He lights explosives and the chamber caves in.

Still in combat, Sydney and Irina end up on a roof deck. Sydney then kicks Irina and she falls on top of a glass roof. When Syd urges her mother to crawl back to her since the glass roof can't hold her weight, Irina insists on grabbing the Rambaldi sphere that rolled a few inches away from her. As she moved forward, the glass shattered and Irina falls through the roof, and dies.

In Mongolia, half of Sloane's body is buried underneath the rubble and is alive -with no one around to hear his calls for help. He talks to Nadia's ghost, who tells him that now, he has all the time in the world and she will not be there to keep him company. She disappears.

Years later, a 7-yr old Isabelle plays by the ocean. As Dixon arrives, Vaughn and Syd emerge out of their beach home to greet him. When Dixon asks Syd for some help in an assignment, Vaughn suggests discussing this after dinner. Meanwhile, Isabelle finds wooden building blocks -the same ones that Sydney played with that made Jack realise Sydney's innate aptitude for being an agent. Isabelle assembles the blocks effortlessly and runs out with Sydney, Vaughn and Dixon for a walk by the beach.