The Rasweilers, married 32 years, have a son and two daughters. For the entire family, an excruciating sense of powerlessness took hold. None of them could bear to sit and wait -- even after Susan learned that Mark had placed a call to a friend from his office at 8:40 a.m. Caryn Wiley, one of the daughters, worked in an advertising firm. She and her husband bolted to the company's art department and ran off 300 copies, then 500 more, of a simple ''Missing'' placard. It gave basic details and little more: every possible variation of his name, his height and weight and three different phone numbers to call. The poster also included a color photograph: Rasweiler, a balding, hale man with oval spectacles and white whiskers, clearly on his way somewhere. A man without aversions, by the look of him. The photograph's background had been cropped out so that it was tightly focused on his face. Suspended in perfect white, he seemed to be in the middle of some grand and ordinary joy. I later learned that the photo had been snapped at a wedding in June. ''We were smiling and laughing,'' his wife said. ''We were feeling like we were going to grow old together. Well, I guess we did grow old together . . . but not old enough.''

At wits' end, the Rasweiler children rushed to hospitals, shelters and anywhere else they could think of, posting fliers on every flat surface, anywhere that made remote sense. Nobody had ever seen such posters in this situation. Everyone wanted a copy; everyone wanted to post it. A homeless man took one to show around. A firefighter taped one to his jacket. In accordance with the surreal laws that govern these situations in Manhattan, Wiley ran into the actors Matthew Broderick and Sarah Jessica Parker, who also took up the cause.

Among other anxious relatives affected by the attack, the ''Missing'' ritual spread swiftly. And bit by bit, the posters expanded in detail. Friends of Lucy Crifasi, a 51-year-old consultant who was working six floors below Rasweiler, for American Express, had printed hundreds of fliers before noticing that others mentioned what possible victims had been wearing. They scrapped the first batch, found a newer photo and made hundreds more copies, this time including Crifasi's last known attire as well as information that might be helpful in unthinkable circumstances: that Lucy had a tiny scar at the center of her forehead and a mole on her jawbone and that there was ''a four-inch scar on either her left or right foot.''

Lucy Crifasi's friends could not have wished for more reach. Relatives phoned from as far as Venezuela, having glimpsed the poster on CNN. The last time I spoke to a friend of Lucy's named Sandra Ciccone, she was still imploring me to display Lucy's picture anywhere I could. This was 12 days after the attack. ''Anything you can do, anywhere you can show this, please do it,'' she said. ''Someone may have seen her.''

Inevitably, the family members who devised the posters -- like the Greeks who sculptured graves for their dead -- had chosen the happiest images they could find, that one perfect moment lived out one final time before the end of things. So the missing people stood smiling in wedding pictures; they were poised above birthday cakes, with babies and puppies and at graduations. The family of Lindsay Herkness III, a Morgan Stanley executive, used various greeting cards he had made last Christmas, each of which bore a picture of him with a joke caption. He was getting into all kinds of amusing situations: now on vacation among a bunch of sheep; now wearing an apron and jovially waving an egg whisk. At the bottom of each came a punch line, like ''Soufflés collapse when you slam the oven door!'' But in the center of each of the cards, in black, someone had stamped ''Missing.''

Desperation and empty time had been conspiring to create other customs all over the city. At Washington Square Park, public expressions of sorrow coalesced around the fence surrounding the great arch. Within days after the attack, it was swathed in immense white canvases and, on its northern side, a giant American flag. All of these -- the flag included -- served as vast communal parchments, and hardly a square inch of space was not crowded by a fury of written gratitude or bewilderment, pacifism or unbridled rage.

With each passing hour, new personal, religious and political exclamations further darkened the cloths. They were palimpsests. One remark was expunged or amended by a different author, whose own statement was in turn refuted just as passionately. It was a rain forest of text, where every bit of soil was a point of struggle. Under ''Osama Wanted: Dead,'' you could just make out ''Islam Is Not the Enemy'' and, in a more ornate script, ''Lives Are Lost but Angels Gained!'' The only commonality to be found was the fact that all this rhetoric existed in a single place. And that basic fact seemed, near enough, a kind of raw harmony.