With the problem of breaching Vault 79 resolved, Paige moves on to the next problem on the list: Defeating the laser grids protecting the gold. Schematics indicate the laser grid is a high-powered, military-grade system that will send the facility into lockdown if the most minute fluctuations in power occur. Paige will forward the residents to Jen, one of the youngest members of the Foundation community, who has come forward and volunteered to solve the problem of penetrating the laser grid in Vault 79.
Jen is located at the Founder's Hall and will explain that she wants to find a suit of Chinese stealth armor, whose stealth field should be able to hide the wearer from the laser grids, allowing them to pass through undetected - much more elegant and reliable than trying to cut the lines and dealing with security redundancies. She will reveal that she knows the technology, but won't reveal anything more.
With Intelligence 12+, the player character can suggest nothing is untraceable, which will result in Jen explaining that she wants to use a small vulnerability in the technology to track it down: Other Chinese devices could detect the suit and report its location back to the controllers, to ensure no spy went rogue.
As such, she asks the player character to travel to the area around Vault 76 where they must collect a Liberator robot and bring it back to her (Liberators are networked and ping each other whenever they see something interesting, a flaw in their design). Once the Liberator is destroyed, and its body recovered, the player character can return to Foundation.
With the help of Penelope Hornwright, Jen manages to find the information she requires, from logs starting in '58 and continuing until roughly 2092. They manage to isolate a single entry, which Jen - fluent in Chinese - interprets as a reference to the Whitespring Resort, and the two figure out that the whole string refers to the 7th hole of the Whitespring golf course. Penny figures out that this means Jen has ties to Chinese secret operations on American soil. Jen explains that both of her parents were Chinese spies, but she was born after the war and has no real ties to China. Penny jumps at the chance to work with cutting edge Chinese technology, and Jen promises noncommittally that she will give her that chance (biometric security on the suit notwithstanding).
To continue the quest, the player character has to head over to the Whitespring and release the robot at the 7th hole and follow it westwards to a nearby entrance to an underground passage. Jen will chime in through the Pip-Boy, explaining that the Foundation settlers and Paige are taking the revelation well, and will leave the settlement to join the player character once they're near the target location. Penny will take over once the player character enters the Deep. The target is inside the secret Chinese base underground, on the bottom floor, in the auxiliary control room.
Inside, Agent Mochou, Jen's mother, is found. She will ask the player character to hold fire and explain that she is not at the base of her own, free will. The player character can ask her questions about her background or the base, but she will only divulge the essentials, promising to expand on them later, if she survives. Jen arrives shortly afterward, surprised to see her mother alive - she thought her dead after her disappearance and already buried her father with his stealth suit after he was killed.
Jen is initially hostile to her mother for abandoning her in the past, but the player character can convince her to give her a chance with Charisma 8+. Jen will agree that this plan can work and Mochou will explain that she can try shielding the signal from the suit but explain that the only way for her to ghost her controllers is to destroy the suit permanently. With Intelligence 12+, the player character can suggest that Penny Hornwright can create tracking countermeasures.
Alternatively, the player character can let the situation unfold, which can lead to Jen becoming permanently estranged from her mother. Or just shoot the Chinese spy in the face, which will advance the quest, yield the stealth suit plans, but also annoy Jen to no end.
If the player character fought the leader of the Chinese soldiers, a commander in power armor, one can take a key from their remains which opens a door within the facility. The room reveals a high tech mining robot known as the Motherlode. It can transport the player character to the Mire or one of several locations in the Savage Divide.
Returning to Foundation and speaking with Jen and Paige once more will conclude the quest. If the player character chooses to spare Mochou, Jen will explain that her mother will join them after the Vault 79 heist, to minimize the danger to Foundation, and will also reassure the player character that the little Liberator will be fixed up by Penny as Foundation's pet. Paige will move on to the next item on the docket: The laser turrets.