When Henry Hook was fourteen years old, living in East Rutherford, New Jersey, his grandmother gave him a crossword jigsaw puzzle for Christmas. Designed by Eugene T. Maleska, who became a legendary editor of the Times crossword, the puzzle had three parts. First, you had to solve the crossword puzzle on paper; then you had to fit the jigsaw pieces together in order to verify your answers. When you were done, if you looked carefully you could find a secret message zigzagging through the answers: “YOU HAVE JUST FINISHED THE WORLD’S MOST REMARKABLE CROSSWORD.” Hook was less than impressed. Within a matter of days, he sent a rebuttal puzzle to Maleska. It contained a hidden message of its own: “⁠WHAT MAKES YOU THINK YOUR PUZZLE IS MORE REMARKABLE THAN MINE?”

In the thirty-two years since then, Hook has come to be known as the Marquis de Sade of the puzzle world: a brilliant and oddly beloved misanthrope, administering exquisite torture through dozens of puzzle books and syndicated crosswords. But he’s not used to being clueless himself. Standing at the corner of Forty-third Street and Ninth Avenue one Saturday night, glaring out from beneath a Brooklyn baseball cap, he looks both fearsomely focussed and a little disoriented. He’s been brought here, along with a team of other puzzle experts, by a blank scroll of paper—the first clue in an elaborate treasure hunt known as Midnight Madness. From Fortieth Street to Sixtieth Street and from the East River to the Hudson, fifteen teams are scrambling across Manhattan in search of clues, each of which points to another location. Every fifteen minutes, teams can call in to headquarters and ask for a hint; the first team to reach the last location wins.

Half an hour ago, one of Hook’s seven teammates pulled out a tape measure and found that the blank scroll was exactly forty-three by nine inches. That brought them to this intersection, where they’ve been searching ever since. Across the street, a writer for “Who Wants to Be a Millionaire” and a crossword virtuoso named Ellen Ripstein are scrutinizing graffiti in a phone booth. Catercornered to them, the editor of the Wall Street Journal crossword is standing beside a professional palindromist who is riffling through a bin of adult-education pamphlets. But by now they’re not alone. All around them, spindly cryptologists from fourteen other teams are scanning signs and peering sharply at Chinese menus. Hook’s teammates already look winded—they’re accustomed to more sedentary puzzle-solving—but their opponents are dismayingly sprightly. They are also better prepared: one team has come with nearly twenty members, many of them dressed in black, who are being deployed like ninjas around the intersection.

Hunts like this are the X-Games of cryptology: half wordplay and half extreme sport. The clues are as much as a mile apart, and the organizers—three shadowy figures known to us only by their first names—seem more interested in absurdist humor and elaborate effects than in pure deductive logic. “I hope you know I’m missing my karaoke night for this,” Hook mutters, lumbering past. Given his reclusive ways, it’s a wonder he agreed to join at all, and it’s clear that he expects to regret it. The T-shirt he’s wearing shows a man with thick spectacles irately crumpling an I.Q. test. “Why am I doing this?” the man is saying. “Why am I allowing myself to be humiliated by these moronic puzzles?!”

Before long, Hook’s team is so desperate for a clue that the writer for “Who Wants to Be a Millionaire” begins quizzing a local panhandler and calling in random guesses to headquarters. Finally, during one call, someone tosses him a lifeline: “Fearless, brave, bold, courageous, valiant, heroic, daring, resolute, audacious, plucky.” The puzzlers glance up at one another with twisted grins: at long last, some words. Then they charge off, as one, for the Hudson.

I first met Hook at the 2001 American Crossword Puzzle Tournament, in Stamford, Connecticut, the largest gathering of puzzlers in the world. (This year is the twenty-fifth anniversary of the event, which will be held from March 15th through the 17th.) More than fifty million Americans solve a crossword at least occasionally, making this by some accounts the most popular indoor pastime in the country. Of these, an élite three hundred and fifty or so come to Stamford every year. In the lobby of the local Marriott, you can see them slumped in armchairs and hunched over coffee tables, playing newly invented board games and odd variations on charades. In the hallways, venders peddle puzzle books, crossword art, and a custom-made crossword Barbie, complete with miniature clue sheets, grids, and pencils. When one puzzler saw me wandering around a little befuddled, he swept his arm across the room as if he were a ringmaster: “Welcome to Weirdoland!”

Joshua Kosman, a classical-music critic for the San Francisco Chronicle, is a typical attendee. “The past fifteen years, for me, has been a process of sinking into, codifying, and coming to terms with the fact that this is what I do. That I’m a puzzle guy,” he told me. Then he cut to the chase: “Did you know that Britney Spears has signed a big endorsement deal with Pepsi? That’s right, it’s true, and we are all very happy about it. You see, ‘Pepsi-Cola’ is an anagram of ‘Episcopal’ and ‘Britney Spears’ is an anagram of ‘Presbyterians.’ ” He paused to let this sink in, but my reaction wasn’t quite what he had hoped for. “Yeah, I know,” he said. “ ‘Episcopal’ is singular, and ‘Presbyterians’ is plural. But we take what we can get.”

For nearly a hundred and twenty years, people blessed with such minds have found one another through the National Puzzlers’ League, which publishes a monthly newsletter called The Enigma. The three hundred and fifty-odd members of the league go by code names that are themselves often miniature puzzles: Kosman’s is Trazom (Mozart backward); a member named Ilene goes simply by I, because the italics make the “I” lean. Over time, the league’s ranks have fissured into the usual sects and denominations: rhyming riddlers, acrostic enigmatologists, and the like. But crosswords are the common denominator, and in Stamford the participants are sorted into a single, ruthless hierarchy.

It wasn’t always so. Not long after crosswords were invented, by an editor at the New York Sunday World, in 1913, The Enigma called for an “anti-toxin to prevent people from taking this dread disease.” The new puzzles were an “inane mental exercise”—glorified quiz sheets for woolly-headed dictionary lovers. But, with time, crosswords grew more intricate and demanding, and puzzlers now reserve their contempt for Scrabble fanatics. Competitive Scrabble is all about memorizing lists of two-, three-, and four-letter words, puzzlers say. But rote memorization won’t help you in Stamford. There, everyone sits at cafeteria-style tables in the ballroom, filling in grids while a giant clock ticks away onstage. Invariably, the same hands dart up first, followed, at predictable intervals, by batches of also-rans and then the rest of the rumbling herd. “I’ve done over nine hundred crosswords in the past three months to get ready for this,” a kindly, silver-haired puzzler from Pennsylvania named Carolyn Bartlebaugh told me. “I’ve just saturated my brain with two-toed sloths and so forth.” But she didn’t expect to gain much ground. “If I can crack the top hundred, I’ll be happy,” she said.