In a hidden alcove off Brigita Gessner’s sealed lab, Robert Langdon studies the elevator’s alphanumeric keypad and replays the previous night’s tense meeting with Gessner at the Four Seasons bar after Katherine Solomon’s lecture.

In the booth, Gessner belittles noetics, needles Katherine about leaving neurochemistry for “metaphysics,” and admits she mainly booked Katherine as a last-minute replacement. Gessner presses to see Katherine’s manuscript and pushes a nondisclosure agreement for a private lab tour. As Katherine grows visibly intoxicated from a powerful Bohemian absinthe, Gessner boasts about a passcode tied to her anti-PSI stance: she claims her lab password is “PSI,” but encrypted as “an Arabic tribute to an ancient Greek with a little Latin twist,” and she insinuates the odds of guessing it are nearly impossible. Langdon deduces from her math that it is a seven-character alphanumeric code.

Back in the suite that night, Langdon’s irritation turns into obsession. He reasons that “Arabic” likely means numbers, and “ancient Greek” points to Archimedes and pi, leading him to write 314159 after removing the decimal. He still cannot account for the “Latin twist,” and he finally sleeps—only to be awakened hours later by Katherine screaming from a nightmare.

Returning to the present in the alcove, Langdon hears Pavel curse on the other side of the wall and run off, likely to find Captain Oldrich Jane1 ek. Langdon considers slipping away but refuses to leave without Katherine, fearing something has happened to her, and focuses again on the keypad with fresh insight.

Langdon realizes the “Latin twist” is literal: the twisting curve of the Latin letter S, turning PI into PSI. He enters 314S159 and, after a brief delay, the elevator activates and opens. Langdon steps into a wood-paneled cabin, but finds no buttons; the doors close on their own and the elevator begins descending, carrying him deeper into Gessner’s hidden lab.