New York ? The most mundane occurrence can resurrect the horror. The floor shudders in the PATH station from subway cars whooshing underneath, and Sue Sisk, getting off a train from New Jersey, can barely stand it: That’s exactly what she felt when the plane hit her tower. Before she can think, she does now what she did then. She runs, as if for her life.

Their minds wander inexplicably. Peter Totten, who escaped from the World Trade Center only to learn that 13 colleagues didn’t, caught himself counting chairs at a table at a wedding reception. Amid dancing and dining, he winced when he realized there were 13. “If they just kind of took that table away, that would be equivalent to what just happened to us,” he thought.

They see the world differently, even from people standing beside them. Walking near Wall Street the other day, Paula Sandiford shuddered at the sight of hundreds of tourists waiting to look into the chasm known as Ground Zero. To them, it is history. To her, it is an open grave belonging to Anthony, Oleh and Luis, co-workers who were sitting alongside her that morning. Two women approached with a camera. “Can you take our picture?” they asked. She looked at them, stunned. “No, I cannot,” she said.

Class unto itself

They are different now, and different from everyone who wasn’t there, as if they were from a country no others have visited. They are trying hard to move on. But it is not so simple. They inhabit a space somewhere between those who died and everyone else.

Estimates of how many people were in the World Trade Center when the attacks began vary from 15,000 to 40,000. This means five to more than 10 times as many people walked out of the twin towers as died in all the Sept. 11 attacks. In the triage of national empathy, grief for the dead has overwhelmed concerns for the merely traumatized. They were the lucky ones, after all. But only by comparison.

They lost friends who sat next to them, had coffee with them, talked shop or laughed with them that very morning. Their families and friends watched on television as planes and flames devoured their buildings, and counted them as surely among the dead. Then they called on the phone or walked in the door, welcomed as something between ghosts and gifts of God.

And now, what are they to do with what Bhanukumar Finavia, drawing on his Hindu beliefs, calls “this extension of life we’ve been given?”

Engineering marvels

The question seems to hang in the air in the temporary offices of Washington Group International, the architectural and engineering firm where Finavia, Sandiford, Totten and Sisk work. The firm had 130 people on the 91st floor of World Trade Center 2 on the morning of Sept. 11. All but 13 survived.

Since late September, most have been back at work. About 60 are stationed on the 32nd floor of 1 Penn Plaza in midtown, with an expansive view of Lower Manhattan they could do without. Others are working in Jersey City where German Miranda, a computer-assisted design specialist, is comforted to look out the window and realize he’s low enough to jump to safety. The company says it plans to reunite them soon, and permanently, in midtown, on a lower floor. It has no view, which suits everyone fine.

On one level, everyone is back on task  developing maintenance schedules for bridges and tunnels, completing a huge water resource project for the Philippines, designing the next phase of New Jersey’s Hudson-Bergen Light Rail. But just beneath the surface, they feel adrift.

“We really don’t know why we are alive,” says Katy Ilachinski, 71, an architect with the company and its predecessors for 35 years. She can still picture Anthony Portillo, a beloved architect and the father of two young children, getting into one elevator that morning while she took another. She never saw him again. “We don’t have the answers,” Ilachinski says. “Who can say?”

Seeking answers, coping

Some are seeking answers in those they love, who now include, as never before, one another  particularly if they came down the stairs together. Others are looking to their work. But it’s not easy for those carrying on the projects of stars like transportation planner Peter Gyulavary, who died at 44, and civil engineer Ulf Ericson, who at 79 was the oldest person to die in the towers. Some managers have critiqued their work by saying, “Ulf would have done it this way,” or, “Mr. Gyulavary would have wanted this.” Employees wonder aloud, is this guidance or grieving? “We say we’re in the Ulf Period, the Peter Period,” one said.

Somewhere in almost every cubicle is an 8 1/2-by-11 poster with photos of the 13 who died and the heading “In Memory of Our Friends  September 11, 2001.” Totten, an engineering manager and the senior person in the office at the time of the attack, made it on his computer. He left believing he had evacuated everyone.

Everyone is coping differently. Amid the nakedness of their temporary desks and cubicles  files and Rolodexes and books and coffee mugs and family photos and children’s artwork went up in smoke  a large partition in the middle of the office has bloomed into a memorial, with obituaries and photographs of co-workers and inspirational poems.

Goddard said he felt upended when he walked past the pictures. “Those kind of things jerk you back when you’re trying to close that out and say, ‘OK, it’s awful, and we lost good people and friends, but we have to go on,’ ” he said.