Part 1 of this technology-rich dystopian spectacle occupies the whole of the darkened 55,000-square-foot Drill Hall, which the audience enters not from the Armory’s grand, staircased main entrance, but through an inconspicuous rear door on Lexington Avenue. (Herzog and de Meuron wanted to punch a kind of guerilla entry into that brick wall, but the idea was nixed.) Once inside, visitors make their way through almost pitchblack corridors to a ramp that takes them up a few feet to the main attraction: a floor on which are projected their surveilled overhead images, which follow them around like digital puppy dogs. The images come from dozens of overhead cameras, not the tethered drones buzzing around overhead. The phenomenon undoubtedly inspires awe in a few (“awe” was mentioned by the designers as the principle desired effect), but to anyone who’s watched one of the Toms—Cruise or Hanks—trying to flee a crew of totally wired bad guys, those illuminated brackets accompanying moving targets are all too familiar.

Getting to Part 2 involves exiting the Drill Hall through another door on Lexington, turning a corner, and hoofing it down the block to the main entrance on Park Avenue. Upon entering, you’re photographed and your face is matched with surveillance photos that were taken surreptitiously in the Drill Hall. (My match turned out not to be me but a handsomer guy a few seats down at the iPad table where visitors see—or, 40 percent of the time, fail to see—their cover blown.)

Part 2, in a much smaller area of the Armory called the Head House, is much the better part of Hansel & Gretel. It’s less glamorous— simply furnished with big wood tables at which visitors can sit. There they can see how well they’ve been spotted in the Drill Hall, as well as peruse the best item in the show: a timeline of surveillance techniques and events from ancient Egypt (“eyes of the Pharoah,” aka spies) through the proto-computer Turing Machine that broke the Nazis’ “Enigma” code and to weaponized drones currently in use in Afghanistan.

Hansel & Gretel seems made to order for middle-school kids on a field trip; they always find special effects in the dark totally cool. (At $15 a ticket, bringing them in would require a drastically reduced group rate.) The Drill Hall gizmopalooza gives everyone a visceral experience of what it’s like to be watched by unseen forces, and the Head House didactics fill in details about the making of the installation. The problem with the exhibition is that in spite of—or perhaps because of—the expensive light show (the Armory won’t say how much it all cost), its insights into the power and meaning of surveillance are superficial. There’s not much beyond a general vibe that electronic surveillance is bad—and this emanates mostly from from Ai’s history of persecution by the Chinese government. Meanwhile, every time there’s a terrorist attack in the West, pundits wonder why the culprits weren’t more thoroughly and continuously surveilled. The lesson of Hansel & Gretel is that a convincing work of art addressing the conundrum of civil liberties versus public safety can’t merely be a funhouse ride in the shadows.