As Tom sleeps, Liz fires a bullet from the gun he hid under the floor, intending to run the firearm through FBI ballistics testing. Over breakfast, Tom asks Liz about the man who attacked him, but she says it's classified. He's frustrated by all the secrets between them. Red contacts Liz with news. The Chinese have just killed a CIA agent in Shanghai in order to use his fingerprints to decode an intercepted message. The decoding failed, and now legendary Chinese assassin Wujing has hired Red to help. Liz is skeptical, but Red's already submitted her cover identity as a cryptographer to Wujing, who's located in D.C. They'll have to act fast to stop him from killing any more CIA agents.
The FBI believes Wujing's encoded message is an order to kill another CIA asset. They want Liz to go along with Red's plan, but she thinks they're crazy, asking a profiler to spy on a spy killer while posing as a cryptographer - a specialty about which she knows nothing. Ultimately, Liz agrees to go undercover, but only if Red will reveal why he chose her. Rather than respond, Red escorts Liz back to the post office. Meanwhile, three men secretly enter her home to install surveillance equipment. Who's spying on Liz and Tom?
Red has arranged to meet Wujing at the radio station he's using as a front for Chinese government surveillance. Liz will decode the message, which should reveal the name of the next hit. Unfortunately, the Chinese will get the information the same time the FBI does, so whoever reaches the target first wins. Meera supplies an encryption specialist to give Liz all the equipment she needs to pull off her cover and a brand new transmitter that looks like a nicotine patch with a range of 300 yards. In theory, it won't show up on a scan. This is how the FBI will keep tabs on Red and Liz. At the radio station, Wujing's henchman, Van Reibeck, insists on getting a biometric print scan from Liz before allowing her into the inner sanctum. The FBI rushes to wipe her records from every database on the planet before Van Reibeck can access them. Disaster averted.
Van Reiback brings Red and Liz to a bunker buried in the basement of the radio station, where the FBI's tracking devices no longer work. When Wujing explains that his computers are hard-wired to the outside world, Liz realizes she won't be able to send the unencrypted message to the FBI.
Only Red can see Liz's laptop, so she furtively types messages asking him to distract Wujing's men so she can access the computer of his encryption guy, Jin. Red looks at a surveillance screen and starts yelling at Wujing. That van parked across the street is full of FBI agents! What kind of operation is this? Knowing they've been made, Ressler orders his men in the surveillance van to pack up and take off, then readies his insertion team. During the hubbub, Liz manages to insert a flash drive with a remote mirroring program into Jin's computer.
As Liz decrypts the Chinese file, the FBI suddenly gains access to everything on Jin's computer - Liz has passed them a jackpot of classified Chinese files. Now the Chinese and the FBI have their name: civilian architect Henry Cho, who's been helping the CIA bug Chinese government buildings. Wujing is the first to locate the target, and he sends his men speeding to Cho's location in a building under construction.
Wujing announces that someone inside the bunker tipped off the FBI about Henry Cho. Though his first instinct says Liz is the leak, Wujing abruptly turns on Jin, beating him within an inch of his life. As he bleeds on the floor, Jin spies Liz's mirroring chip and realizes she's the leak. Before he can utter a word, Red grabs a gun and shoots Jin dead. Furious, Wujing wants an eye for an eye and trains his gun on Liz, but Red talks him out of it. Ultimately, Wujing leads them out a back door and into a waiting SUV, offering Liz and Red passage out of the country. They decline, and Liz slaps her tracking patch on the car as she's getting out. Moments later, the FBI arrests Wujing and his men.
Just as Meera and Ressler phone Cho and tell him to stay put, a Chinese assassin steps out of the elevator. Cho stashes his young son, then scrambles onto a scaffolding where a game of cat and mouse ensues. Ressler fights off several killers as another one finds Cho's son and takes him hostage. Hearing his son's screams, Cho surrenders and is just about to die when Meera steps in to shoot his would-be killer.
Alone with Red, Liz once again demands to know why he chose her. Red says it's because of her father. What about her father? Red wishes the answer were a simple one, but it's not, and of course he doesn't reply. Liz grows frustrated; she has people who care about her, a life, but what does Red have? "I have you," he says. Back at the post office, Ressler congratulates Liz for saving Cho and apologizes for underestimating her ability as an agent. Liz checks out the ballistics report on Tom's gun, which comes back almost entirely redacted. There may be a match, but that information has been classified by the CIA.
Following Cooper's orders to shadow Liz, Ressler reports back. They know she requested the ballistics report, and they have the unredacted version, which involves a very touchy homicide. Any briefings on the case have to go all the way to the Secretary of Homeland Security. In his hotel suite, Red enjoys a solitary dinner by candlelight. For dessert, he opens an envelope with Chinese writing on it to reveal a number: 042983. Liz returns home to find all their friends have gathered to rally around Tom. He apologizes for hassling Liz about her job, claiming he understands that some things are just classified. As Liz quietly ponders his true motives, a group of men in an apartment across the street studies monitors displaying surveillance feeds from Liz and Tom's place.
Liz and Red go undercover to take down an assassin who's been decimating the ranks of the CIA.