IT'S 8 A.M. on Wall Street, and people toting briefcases are bustling out of subways and into high-rise office buildings. Streets are clean, shops are starting to open, and there's no acrid odor or smoke in the air.

Walk a bit closer to the World Trade Center site, though, and the routine begins to blur. Barriers prevent pedestrian traffic. An American flag drapes an adjacent building. Rescue workers continue their round-the-clock search for the dead.

Such are the contradictions six months after terrorists tore a hole in New York's financial district.

In one sense, Wall Street is digging itself out. Merrill Lynch & Co. executives have returned to the company's headquarters, a stone's throw from ground zero. Stock exchanges and financial firms in the area -- shuttered for four days in September -- have expanded offsite backup systems in case of another catastrophe. Stock markets are rising.

But the recovery is coming in fits and starts. Numbers tell one story: Just 17% of the 137,919 employees displaced by the attacks have returned, according to TenantWise.com, an online real-estate broker. Some Wall Street firms have moved far from Wall Street -- Lehman Brothers Holdings Inc., once a neighbor of Merrill Lynch in the World Financial Center complex across the street from the Twin Towers, has relocated nearly two-thirds of its 6,400 headquarters employees to midtown Manhattan. All told, firms based in downtown New York have moved nearly 30% of their employees, many permanently, outside the city.

The impact of the personal tragedy is impossible to quantify. Nowhere is that more evident than at four financial firms with offices in the World Trade Center that were among the most devastated in the destruction. It's these firms -- Cantor Fitzgerald LP, Fred Alger Management Inc., Sandler O'Neill & Partners and Keefe, Bruyette & Woods Inc. -- whose victims accounted for nearly one-third of the 2,830 who died at the Twin Towers on Sept. 11 -- where the healing has been hardest.

In the immediate aftermath of the attacks, Wall Street pulled together. Jefferies Group Inc. donated $6.5 million, its trading revenues and commissions generated on Oct. 11, to firms, including Sandler O'Neill. Cisco Systems Inc. rewired Cantor Fitzgerald's makeshift offices in New Jersey, sending equipment and crews without any talk of the cost. And Merrill brought Sandler O'Neill and Keefe Bruyette into the group of securities firms distributing a stock offering for Allied Capital Corp. on Sept. 24.

"I felt like I was standing in the soup line," recalls John Duffy, Keefe's chairman. "We were grateful for what we got, but we didn't want to be there."

Now, the adrenaline rush that pushed employees to carry on amid such tumult has long since ebbed. As Billy Joel sang in "New York State of Mind": It comes down to reality. And these days, that means competing in a tough business in the harshest business environment in years. So even as financial firms have pulled themselves up -- and in many cases, managed to perform remarkably well -- there are constant reminders of Sept. 11.

Many employees simply can't talk about what happened. A phrase will trigger memories of a lost colleague. Some have stashed away pictures of associates who were victims, unable for now to deal with the pain. And at Merrill and other firms with offices still abutting the former trade center, there is the constant pall of what happened that sunny late-summer morning. They need more than blinds on their windows to shut it all out.

But make no mistake: Wall Street is rebuilding. As spring approaches, there are new beginnings. On Monday, Alger Management will move into new offices about 2-1/2 miles north, near Union Square. And at ground zero, two temporary memorials will be unveiled: a 45,000-pound bronze sculpture retrieved from the World Trade Center plaza and a sculpture of light consisting of two columns resembling the Twin Towers.