China intends to mount a microwave laser on a satellite as an assassination weapon. It would make the victim appear as if he died of natural causes. He wants Syd to accompany him and corrupt the data. Syd will access the motherboard, connect to Marshall, who will corrupt the system.

Vaughn and Lauren travel Mexico to interview Javier. Jack advises Vaughn to impede the investigation. Vaughn disagrees, saying Lauren is their best chance to keep Syd's secret from NSC. Syd and Sloane attend the Beijing ball posing as lovers. Syd secretly assembles a toy car controlled by Marshall, which he uses to follow a guard to the security system. Sloane persuades Syd to dance for the sake of their cover. Marshall shuts down the system. Syd gladly slaps Sloane in order to give the impression they're having a lover's spat.

Meanwhile, Jack has bribed the Mexican police to detain Vaughn and Lauren. When they're released, they find Javier dead in his cell, an apparent suicide victim. Vaughn tells Jack if he ever puts his wife in danger again, he'll kill him. Jack tells Vaughn that maybe now he understands the compromises one makes when a loved one is in danger.

Syd finds the vault, retrieves the case and connects to it, allowing Marshall to corrupt the code. The guards repair the security system and spot Syd. She fights off the guards as Marshall finishes his job. Afterward, Sloane says the day she was found in Hong Kong, he received a letter in Syd's handwriting, address to Sydney Bristow. He gives it to her. A key and paper fall out. It's a series of numbers, a code.

Sark pays a visit to Lauren. He says that he had planned for Javier to be extradited and forced to confess the identity of Lazarey's murderer. He gives her a dossier, which includes a picture of Lazarey and Julia Thorne. Sark identifies Thorne as Sydney.

Jack looks at the note Sloane gave Syd. He says the cipher text was devised by Irina. It's the address of a penthouse in Rome.

Vaughn and Lauren argue about keeping Sydney's secret. He says Dixon ordered him not to divulge anything, but she'll have none of it. Vaughn says Lindsey will ship Syd off to Russia if he finds out. Lauren admits that she's already reported Syd. Vaughn then tells Syd everything and arranges for her to fly to Rome and pick up a new passport.

Syd asks him why he's helping her. He says some things don't change. "I'm not going to lose you twice," he says, and they hug. Later, Vaughn tells Jack he'll do anything to help Syd. Under Lindsey's authorisation, Lauren takes control of the task force from Dixon, relieving him for "obstruction of justice."

Syd enters her apartment in Rome. Through the window, she sees the figure she dreamt of. She searches the medicine cabinet and finds a bottle is prescribed to Julia Thorne. The Italian police barge in.