Langdon presses Katherine about the “even bigger reason” the CIA might have to destroy her manuscript. Katherine explains that her late Princeton adviser, Professor Cosgrove, unusually insisted she file a patent application as an “educational exercise” for her artificial-neuron concept, even though he expected it to be denied as unbuildable. In hindsight, Katherine suspects Cosgrove was protecting her because he somehow knew her thesis was being secretly appropriated.

Katherine reveals that her own copies of the rejected patent application later vanished, but Cosgrove kept one. After Cosgrove died, his sister delivered a sealed envelope containing the faded, intact application to Katherine, giving her proof and leverage. Langdon urges they leave immediately, fearing the CIA could still discover and seize that last copy at Katherine’s home.

Katherine then admits the most dangerous detail: while writing the final chapter of her noetics manuscript, she decided to include the entire fourteen-page rejected patent application—stamped “DENIED”—to inspire young scientists. Langdon realizes this would effectively publish blueprints for Threshold’s stolen human-to-machine breakthrough, creating legal and political peril for the CIA and threatening its monopoly and potential profit. Katherine also connects this to Brigita’s questions about patents and why Finch likely panicked when Katherine denied ever applying for one.

Using the classified binder, Katherine shows Langdon PALM imagery of an implanted brain: a large chip embedded in tissue with a cord leading to a fluorescent neural mesh. The pages identify the subject as “PATIENT #002 / VESNA,” confirming Sasha Vesna has the implant. Katherine notes the binder focuses on integration data and is baffled that Threshold appears to have accelerated chip-to-brain integration far faster than biology should allow.

Langdon and Katherine search for “patient number one” and find a short section labeled “PATIENT #001 / SYSEVICH,” with an implanted-brain image and a headshot, but almost no post-op follow-up data—suggesting something went wrong, possibly death. As they try to leave, lights suddenly blaze in the RTD hallway, signaling someone is approaching; Finch’s POV confirms he has noticed signs of intrusion and the RTD corridor lights turning on.

Trapped in a dead end, Katherine spots forklift tire marks leading into the far wall. She and Langdon sprint to an electric-eye sensor that triggers a hidden sliding wall, opening into a colder, dark corridor; they slip through just before it closes. Soft light reveals they are at the top of a concrete ramp spiraling down a narrow shaft, showing Threshold extends farther than they knew—deeper underground.