“The sticker,” Winston replied in Langdon’s head, “is not one I recognized, but I compared its shape to all known symbols in the world, and I received a single match.”

Langdon was amazed how fast Winston had been able to make all this happen.

“The match I received,” Winston said, “was for an ancient alchemical symbol—amalgamation.”

I beg your pardon? Langdon had expected the logo of a parking garage or a political organization. “The car sticker shows the symbol for … amalgamation?”

Fonseca looked on, clearly lost.

“There must be some mistake, Winston,” Langdon said. “Why would anyone display the symbol for an alchemical process?”

“I don’t know,” Winston replied. “This is the only match I got, and I’m showing ninety-nine percent correspondence.”

Langdon’s eidetic memory quickly conjured the alchemical symbol for amalgamation.

“Winston, describe exactly what you see in the car window.”

The computer replied immediately. “The symbol consists of one vertical line crossed by three transverse lines. On top of the vertical line sits an upward-facing arch.”

Precisely. Langdon frowned. “The arch on top—does it have capstones?”

“Yes. A short horizontal line sits on top of each arm.”

Okay then, it’s amalgamation.

Langdon puzzled for a moment. “Winston, can you send us the photo from the security feed?”

“Of course.”

“Send it to my phone,” Fonseca demanded.

Langdon relayed the agent’s cell-phone number to Winston, and a moment later, Fonseca’s device pinged. They all gathered around the agent and looked at the grainy black-and-white photo. It was an overhead shot of a black sedan in a deserted service alley.

Sure enough, in the lower-left-hand corner of the windshield, Langdon could see a sticker displaying the exact symbol Winston had described.

Amalgamation. How bizarre.

Puzzled, Langdon reached over and used his fingertips to enlarge the photo on Fonseca’s screen. Leaning in, he studied the more detailed image.

Immediately Langdon saw the problem. “It’s not amalgamation,” he announced.

Although the image was very close to what Winston had described, it was not exact. And in symbology, the difference between “close” and “exact” could be the difference between a Nazi swastika and a Buddhist symbol of prosperity.

This is why the human mind is sometimes better than a computer.

“It’s not one sticker,” Langdon declared. “It’s two different stickers overlapping a bit. The sticker on the bottom is a special crucifix called the papal cross. It’s very popular right now.”

With the election of the most liberal pontiff in Vatican history, thousands of people around the globe were showing their support for the pope’s new policies by displaying the triple cross, even in Langdon’s hometown of Cambridge, Massachusetts.

“The U-shaped symbol on top,” Langdon said, “is a separate sticker entirely.”

“I now see you are correct,” Winston said. “I’ll find the phone number for the company.”

Again Langdon was amazed by Winston’s speed. He’s already identified the company logo? “Excellent,” Langdon said. “If we call them, they can track the car.”

Fonseca looked bewildered. “Track the car! How?”

“This getaway car was hired,” Langdon said, pointing to the stylized U on the windshield. “It’s an Uber.”

CHAPTER 26

FROM THE LOOK of wide-eyed disbelief on Fonseca’s face, Langdon couldn’t tell what surprised the agent more: the quick decryption of the windshield sticker, or Admiral Ávila’s odd choice of getaway car. He hired an Uber, Langdon thought, wondering if the move was brilliant or incredibly shortsighted.

Uber’s ubiquitous “on-demand driver” service had taken the world by storm over the past few years. Via smartphone, anyone requiring a ride could instantly connect with a growing army of Uber drivers who made extra money by hiring out their own cars as improvised taxis. Only recently legalized in Spain, Uber required its Spanish drivers to display Uber’s U logo on their windshields. Apparently, the driver of this Uber getaway car was also a fan of the new pope.

“Agent Fonseca,” Langdon said. “Winston says he has taken the liberty of sending the image of the getaway car to local authorities to distribute at roadblocks.”

Fonseca’s mouth fell open, and Langdon sensed that this highly trained agent was not accustomed to playing catch-up. Fonseca seemed uncertain whether to thank Winston or tell him to mind his own damn business.

“And he is now dialing Uber’s emergency number.”

“No!” Fonseca commanded. “Give me the number. I’ll call myself. Uber will be more likely to assist a senior member of the Royal Guard than they will a computer.”

Langdon had to admit Fonseca was probably right. Besides, it seemed far better that the Guardia assist in the manhunt than waste their skills transporting Ambra to Madrid.

After getting the number from Winston, Fonseca dialed, and Langdon felt rising confidence that they might catch the assassin in a matter of minutes. Locating vehicles was at the heart of Uber’s business; any customer with a smartphone could literally access the precise locations of every Uber driver on earth. All Fonseca would need to do was ask the company to locate the driver who had just picked up a passenger behind the Guggenheim Museum.

“¡Hostia!” Fonseca cursed. “Automatizada.” He stabbed at a number on his keypad and waited, apparently having reached an automated list of menu options. “Professor, once I get through to Uber and order a trace on the car, I will be handing this matter over to local authorities so Agent Díaz and I can transport you and Ms. Vidal to Madrid.”