“Furthermore, when you asked why I wouldn’t just walk around with you in person, I gave you an accurate answer about Mr. Kirsch wanting to keep museum crowds small. But that answer was incomplete. There is another reason we are speaking via headset and not in person.” He paused. “I am, in fact, incapable of physical movement.”

“Oh … I am so sorry.” Langdon imagined Art sitting in a wheelchair in a call center, and regretted that Art would feel self-conscious having to explain his condition.

“No need to feel sorry for me. I assure you legs would look quite strange on me. You see, I’m not quite how you imagine.”

Langdon’s pace slowed. “What do you mean?”

“The name ‘Art’ is not so much a name as it is an abbreviation. ‘Art’ is short for ‘artificial,’ although Mr. Kirsch prefers the word ‘synthetic.’” The voice paused a moment. “The truth of the matter, Professor, is that this evening you have been interacting with a synthetic docent. A computer of sorts.”

Langdon looked around, uncertain. “Is this some kind of prank?”

“Not at all, Professor. I’m quite serious. Edmond Kirsch spent a decade and nearly a billion dollars in the field of synthetic intelligence, and tonight you are one of the very first to experience the fruits of his labors. Your entire tour has been given by a synthetic docent. I am not human.”

Langdon could not accept this for a second. The man’s diction and grammar were perfect, and with the exception of a slightly awkward laugh, he was as elegant a speaker as Langdon had ever encountered. Furthermore, their banter tonight had encompassed a wide and nuanced range of topics.

I’m being watched, Langdon now realized, scanning the walls for hidden video cameras. He suspected he was an unwitting participant in a strange piece of “experiential art”—an artfully staged theater of the absurd. They’ve made me a rat in a maze.

“I’m not entirely comfortable with this,” Langdon declared, his voice echoing across the deserted gallery.

“My apologies,” Winston said. “That is understandable. I anticipated that you might find this news difficult to process. I imagine that is why Edmond asked me to bring you in here to a private space, away from the others. This information is not being revealed to his other guests.”

Langdon’s eyes probed the dim space to see if anyone else was there.

“As you are no doubt aware,” the voice continued, sounding eerily unfazed by Langdon’s discomfort, “the human brain is a binary system—synapses either fire or they don’t—they are on or off, like a computer switch. The brain has over a hundred trillion switches, which means that building a brain is not so much a question of technology as it is a question of scale.”

Langdon was barely listening. He was walking again, his attention focused on an “Exit” sign with an arrow pointing to the far end of the gallery.

“Professor, I realize the human quality of my voice is hard to accept as machine-generated, but speech is actually the easy part. Even a ninety-nine-dollar e-book device does a fairly decent job of mimicking human speech. Edmond has invested billions.”

Langdon stopped walking. “If you’re a computer, tell me this. Where did the Dow Jones Industrial Average close on August twenty-fourth, 1974?”

“That day was a Saturday,” the voice replied instantly. “So the markets never opened.”

Langdon felt a slight chill. He had chosen the date as a trick. One of the side effects of his eidetic memory was that dates lodged themselves forever in his mind. That Saturday had been his best friend’s birthday, and Langdon still remembered the afternoon pool party. Helena Wooley wore a blue bikini.

“However,” the voice added immediately, “on the previous day, Friday, August twenty-third, the Dow Jones Industrial Average closed at 686.80, down 17.83 points for a loss of 2.53 percent.”

Langdon was momentarily unable to speak.

“I’m happy to wait,” the voice chimed, “if you want to check the data on your smartphone. Although I’ll have no choice but to point out the irony of it.”

“But … I don’t …”

“The challenge with synthetic intelligence,” the voice continued, its light British air now seeming stranger than ever, “is not the rapid access to data, which is really quite simple, but rather the ability to discern how the data are interconnected and entangled—something at which I believe you excel, no? The interrelationship of ideas? This is one of the reasons Mr. Kirsch wanted to test my abilities on you specifically.”

“A test?” Langdon asked. “Of … me?”

“Not at all.” Again, the awkward laugh. “A test of me. To see if I could convince you I was human.”

“A Turing test.”

“Precisely.”

The Turing test, Langdon recalled, was a challenge proposed by code-breaker Alan Turing to assess a machine’s ability to behave in a manner indistinguishable from that of a human. Essentially, a human judge listened to a conversation between a machine and a human, and if the judge was unable to identify which participant was human, then the Turing test was considered to have been passed. Turing’s benchmark challenge had famously been passed in 2014 at the Royal Society in London. Since then, AI technology had progressed at a blinding rate.

“So far this evening,” the voice continued, “not a single one of our guests has suspected a thing. They’re all having a grand time.”