Langdon drives an SUV with a manual transmission toward Folimanka Park and the hidden CIA facility, Threshold, while Katherine tries to lighten the mood. Langdon privately worries about why Katherine’s manuscript drew CIA attention and hopes Threshold will provide answers.

As they travel, they discuss whether Threshold could be tied to drug-induced altered states or historic CIA experimentation. Katherine explains her view that some hallucinogens may lower the brain’s “filtering,” but she rejects using drugs herself, warning that psychedelic disruption (especially serotonin dysregulation) can cause lasting harm.

Langdon asks what, if not drugs, might have triggered CIA interest. Katherine points to her experiments in precognition, where test subjects’ brains react to images before a computer randomly selects them; she suggests a model in which choices are “received” from a surrounding consciousness field rather than freely generated. Their debate about free will becomes intimate when Katherine kisses Langdon, framing the “illusion” of choosing as possibly sufficient.

Katherine then connects sex, orgasm (“la petite mort”), and near-death-like self-detachment to the broader noetic idea of out-of-body experience. This leads her to a new suspicion about Sasha, Gessner’s epileptic lab assistant: if Threshold involves remote viewing, epilepsy could be valuable because epileptic brains may more naturally produce OBEs, making them potential remote viewers or ideal study subjects.

Langdon mentions another Russian epilepsy patient, Dmitri, whom Gessner also treated and “cured.” Katherine argues it is unlikely Gessner acted out of compassion and doubts the CIA would release such a subject back to Russia, implying Dmitri may still be controlled or monitored. As they near the park, Langdon focuses on reaching Threshold for confirmation.