Langdon, still shaken by recent gunfire, follows ÚZSI Captain Oldřich Janáček and Lieutenant Pavel through a shattered entry into Crucifix Bastion. Janáček focuses on a locked steel door labeled LAB with a biometric panel and reinforced window, concluding it leads down a stairwell to Gessner’s lab. Finding no way in, Janáček drags a broken safety-glass frame to the door as a makeshift alarm to detect anyone trying to slip out.

Pavel sweeps the adjacent hallway with his gun raised, checking rooms and corners. The search opens into a bright, luxury-like waiting area with sweeping views of Prague and a large, valuable Brutalist wall sculpture that Langdon recognizes as a Paul Evans piece. Janáček moves into Gessner’s open office, but finds it empty; the office is decorated with colorful brain MRI prints that make Langdon reflect on science treated as art.

Janáček uses an intercom to order Dr. Brigita Gessner and Katherine Solomon to come upstairs immediately and confirm they heard him, but no one answers. Janáček points out signs that someone has been there and questions why Katherine would ignore him. He seats Langdon under guard while he makes urgent calls, as Langdon’s unease grows over the silence from below.

While waiting, Langdon recalls Katherine’s recent lecture about the brain’s immense storage capacity, neuroplasticity, and her argument against strict materialism. Langdon reconsiders the Paul Evans sculpture and becomes irritated that it is propped on the floor with a stabilizing bar rather than properly mounted; a new suspicion strikes him, and he stands to approach it.

Pavel abruptly intercepts Langdon and aims a gun at his chest, assuming Langdon is trying to leave. After Janáček calms Pavel, Langdon lies that he was heading to the restroom and sits back down, forced to abandon whatever he thought he had noticed about the artwork.

The chapter then shifts to the Golěm crossing Old Town Square to a taxi. He recalls forcing Gessner to confess that her colleagues built a vast underground complex called Threshold, hidden in the city and accessible only to someone who knows the concealed entrance and has a specialized RFID key card. The Golěm took Gessner’s personal card and left her to die, but discovered the card alone is insufficient; realizing he needs a second item stored in Gessner’s private lab, he orders the taxi to take him to Crucifix Bastion.