As the investigation into Jolene’s death inches dangerously close to Tom, Red alerts Liz to a fatal car accident he suspects is the work of a Russian computer hacker known as Ivan. After Liz and Ressler find plans for a nuclear centrifuge in the wreckage of the car, a team of NSA agents classifies the crime scene, claiming that the victim was working on a top-secret cyberweapon known as Skeleton Key. Now that the weapon’s prototype has gone missing, Red heads to Belarus with Ressler and Meera close behind. When the FBI raids the restaurant where he and Ivan are meeting, Red fakes killing Ressler in order to keep the hacker in the dark about their investigation. But when pressed about the Skeleton Key, Ivan says he didn’t steal it and that the thief is an imposter whom Aram identifies as Harrison Lee, a 17-year-old high school student and computer whiz. Meanwhile, when Jolene’s phone records lead Liz to the secret apartment they used for their mission, Tom quickly destroys whatever documents he can before fleeing just ahead of her.
When Liz leads a team of agents to Lake Hill High School, Harrison triggers an evacuation alarm and escapes. After Aram learns that he’s been stalking Abby Fisher, a classmate and daughter of the lead engineer on the Skeleton Key project, the power grid in Washington suddenly starts shutting down. As the FBI questions David Fisher, Harrison lures Abby to a Metro station while Tom takes advantage of the blackout to confront Red and threaten to kill Liz if she gets any closer to the truth about him and Jolene.
After Harrison says he took the Skeleton Key to keep her and her dad from moving to Colorado to continue his work, Abby tries to run, but trips and hits her head on the asphalt. Leaving her behind, Harrison boards a Metro train he’s controlling with the Skeleton Key, unaware that Liz is on board, too. Realizing that Harrison is on a suicide mission, Liz persuades him to stop before they crash. With Fisher and Abby reunited and Harrison in custody, Liz heads for home where she finds evidence identifying Tom as the man she saw running away from the safe house after destroying the documents. Finally, when she goes to tell Red that he was right about Tom, she begins to piece together the clues linking him to her father.