University of Chicago student Zak Skinner is failing engineering school—again. He transferred from New York University mere months ago for that same reason. Understandably distraught, Zak runs into David Wade, a floor mate from his dorm, and winds up voluntarily drinking a hallucinogenic concoction. By the time Zak comes to, things have turned noticeably weird. David has seemingly disappeared, and Zak has a simple store receipt with hidden numbers and, perhaps, a secret message. It may all be part of a scam, as someone has been supposedly drugging impressionable freshmen who will believe anything anyone tells them. But that doesn’t explain the thugs who capture Zak and his best friend/roommate, Pat Riley, giving them 24 hours to hand over the receipt. Deciphering the significance of that piece of paper takes Zak deep into a conspiracy linked to a darknet website and billions in American dollars. But answers aren’t easy to come by, as the receipt’s apparent code isn’t clear, and people evade Zak’s myriad questions. Time may be running out, as he’s fairly certain someone is trying to kill him. Towles’ taut novel moves at a steady clip, as the protagonist encounters a variety of odd characters both on and off campus. Regarding the plot, readers may be just as confused as Zak; it’s often cryptic and features someone promising to protect Zak from “villains you can’t see.” But it’s undoubtedly suspenseful, with dubious characters aplenty who occasionally threaten or assault Zak. They’re not all bad; Riley makes a superb sidekick who also finds trouble (mostly by association), and Zak dabbles in some effectively understated romance. While there’s definitely a resolution, along with an enlightening glimpse at the hero’s past, the ending implies that a sequel may be forthcoming.