Langdon arrives by taxi at the snowy base of Petřín Tower, drawn by the message claiming Katherine is being held there. The driver abruptly leaves, and Langdon—alone and anxious—heads into the visitor center, scanning for signs of Katherine or her captor.

Inside, an attendant tells Langdon the tower has just opened and that only two people are currently at the top. With the steep staircase closed for winter, Langdon rides the cramped, rattling elevator upward, regretting he did not take Sasha’s gun and bracing for a confrontation.

At the observation deck, Langdon discovers the two people are simply a young Indian couple taking photos; Katherine is nowhere in sight. He waits in the wind, watching the grounds below and growing increasingly suspicious that the “I have Katherine” note may be a trap rather than a ransom instruction.

When the couple asks Langdon to photograph them, he complies, then requests to borrow the woman’s phone because he has lost his own. Langdon calls the Four Seasons and is told Katherine left the hotel that morning and has not returned; the hotel manager tries Langdon’s suite line but gets no answer, deepening Langdon’s fear that Katherine’s movements after leaving the hotel are unknown.

To search for any message Katherine might have sent, Langdon pretends he is on a private call, then uses the borrowed phone to log into his email. He finds an email from Katherine sent at 7:42 a.m. with a blank subject and blank body but with an attached image; after a tense confrontation with the couple as the file loads, Langdon views the startling, unexpected picture, commits it to memory, closes the browser, returns the phone, and listens as the couple finally descends in the elevator.