Moments after the mysterious explosion, Sophia and Thomas reappear in an alley. Sophia chastises Thomas for putting peoples' lives at risk, but Thomas claims it was their only way of escaping. There's no sign of Simon, so Sophia's left to wonder if he made it out of the building alive. Sophia asks Aaron to investigate. At the White House, Martinez demands to know why Sophia and Thomas always seem to be one step ahead of the government investigation. Sterling admits there's a traitorous informant among them and that his aide Justin Murphy is questioning the field team. Unfortunately, Sterling's lost touch with Murphy; last Sterling heard, Murphy was on his way to question Agent Lee. Frustrated and tired of excuses, Martinez tells Sterling to find the informant immediately - or else.
It's 14 years earlier. Sterling and his wife Laura are preparing a romantic dinner. CIA agent Edmond phones Sterling, interrupting the domestic moment. Edmond tells Sterling to drop everything in order to deal with an urgent matter. Sterling hides his disappointment from Laura, who clearly doesn't know about his job. We're back to the present. Sterling visits Simon in his hospital room. Simon is unconscious so Sterling decides to stand by until he recovers. Outside the coffee shop, agents discover a roughed-up Murphy in the trunk of a car. Murphy tells the agents that Simon is the mole - Sterling must know this at once!
At the Buchanan home, Madeline tries to convince Sean and Leila that Michael was abducted because he knew too much about the extraterrestrial biological entities (E.B.E.s) at Inostranka. Though Madeline isn't sure of the details, she thinks Michael is linked to Flight 514 and the botched presidential press conference somehow. Madeline claims that the night before Michael disappeared, he said that someone would go to any lengths to stop Martinez. Madeline tells Leila that finding out who that person is - and what his motives are - might be the only way to find Leila's family. Sean and Leila reluctantly let Madeline look through Michael's top-secret government files for clues. Madeline immediately finds a list of 13 women's names alongside a strange sequences of numbers. Though she can't crack the code, Madeline says she knows someone who can.
At a gorgeous mansion, Dempsey is tending to his genetically engineered orchid garden when Carter calls. Dempsey's agents have provided Carter with a secure line at a Dallas FBI office; Carter's using this opportunity to let Dempsey know that Leila and Sean have escaped. More troubling to Dempsey is the news that Leila and Sean have figured out that Michael was chosen to fly Flight 514 for a reason. Safely in Thomas' extravagant apartment, Sophia finally loses her temper. She blames Thomas for ruining the trust she'd worked so hard to build with the Martinez administration. Sophia asserts that she's in control. Thomas backs down, saying, "I'm sorry, mother." Aaron interrupts with news that Simon is suspected of being the mole.
Murphy tells Sterling and Agent Garret that Simon is the mole. Murphy claims that when he attempted to test Simon for trace radiation, Simon attacked. Why would Simon have done that if he weren't the informant? Garret passionately refutes Murphy's claims, stating that Simon saved his life back at the imploding building. It's clear Sterling doesn't know what to believe. It's 14 years earlier. Sterling's father Edmond reveals terrible news: Sterling's wife Laura is actually a Russian intelligence operative named Svetlana Agletinova. In order to save his career, Sterling must kill the woman he loves before she steals additional files from him.
We're back to the present. After looking through Simon's file, Sterling's noticed that he has no family members, a mysterious past, and - most alarmingly - hasn't aged at all. Sterling tells Murphy that Simon might not just be the informant - he might also be a sleeper! Sterling asks Murphy to run a blood test on Simon at once. Madeline leads Sean and Leila to Peter, a man Madeline claims can help crack Michael's coded documents. Peter tells Leila that the government is holding Michael but that Samantha is most likely dead. Unbeknownst to Sean and Leila, Dempsey's men - led by Rivas - have just searched the Buchanan home and are hot on their trail! Dempsey (who is hooked up to an IV) tells Rivas to find Sean, Leila and Madeline right away.
In Atlanta, Georgia, a woman in a black SUV fills a syringe with a mysterious liquid. In the backseat, a bound and gagged Samantha looks on in terror. Back at his apartment, Peter discovers that the document is a list of 13 missing girls. They're all about the same age as Samantha. The codes besides the names are ID numbers for shell corporations based in Los Angeles. Suddenly, Rivas and his armed men charge into Peter's building! Sean, Leila, Peter and Madeline escape onto a neighboring rooftop. Peter sets off a huge explosion and in seconds his apartment is destroyed. As soon as the dust settles, Sean and Leila look around, only to find that Peter and Madeline are gone!
Near Simon's hospital room, Thomas (disguised as a nurse) walks into the hematology lab and switches Simon's blood sample with a human sample. Leaving, Thomas shares an elevator with a clueless Sterling, who absentmindedly asks for a cigarette. Thomas doesn't have one, and suggests that dark chocolate will help Sterling kick his addiction. It's 14 years earlier at Sterling's home. Sterling tells Laura that he knows she's a spy. But because he loves her - and because he believes she loves him too - he wants to run away with her to Buenos Aires. Laura sprints out of her bedroom and into her car where Edmond shoots her dead. Edmond gives Sterling the gun and tells him to take credit for this "triumphant" moment in his career.
We're back in the present. Outside the coffee shop, Garret has found the vial used to transport the Scandium-46 (the isotope used to track Sophia). Garret tells Sterling that he's testing two partial prints found on the vial for clues. Whoever handled the isotope is certainly the mole. Simon regains consciousness. Sterling tells Simon that his blood sample proves he's human. As for the vial at the crime scene, it's got Murphy's prints all over it. Therefore, Sterling believes Murphy's the mole. Sterling apologizes to Simon for suspecting him. Meanwhile, Murphy is arrested. We flash back to the coffee house hours earlier. Using fingerprint tape, Aaron lifts Murphy's fingerprint off Murphy's door handle and reapplies it on a vial of Scandium-46. Aaron framed Murphy.
At Thomas' apartment, Thomas tells Sophia that Simon has been cleared. Sophia's relieved, but she's still preoccupied with something. She asks Simon how his plan to "transport everyone home" is progressing. Though Thomas has some material, he still needs additional components. The raw material he needs is in tightly guarded nuclear warheads. He tells Sophia he might have a way in... At the Oval Office, Martinez watches a news report claiming that the Flight 514 passengers are fully recovered and will be released shortly. Sterling enters Martinez's office and apologizes for being so wrong about Murphy. "I failed you, sir. I'm sorry," Sterling says. Martinez accepts Sterling's apology, claiming it's almost a relief to find out that Sterling isn't perfect.
The woman we saw in the black SUV leads a frightened Samantha down a menacing hallway and into a playroom. Little girls play with toys and hardly seem to notice Samantha's presence. "Girls, this is Samantha," the woman says. Suddenly one of the little girls turns around revealing an aged, wrinkled face! Samantha looks at her new playmates in terrified silence.