Ed Breen showed up for his first day of work at the midtown Manhattan headquarters of Tyco International at 7:30 on a late July morning two years ago. He'd been hired the previous week to succeed CEO Dennis Kozlowski, who'd resigned in early June. He rode the elevator to the 43rd floor and stepped out. The office was unnervingly quiet. "There was nobody there," Breen recalls.

It was the last hour of calm that Breen would enjoy for more than a year. He was about to be consumed by what he calls "the swirl" -- a series of investigations, firings, restructurings, board battles, and financing events that felt not just chaotic but at times completely unmanageable. "It was a constant barrage of surprises," Breen says. "Every day, you'd pick up the paper and the company was being trashed." Most days, there were more attorneys and SEC investigators in the office than Tyco executives.

Breen, former president of Motorola, had walked into a firestorm: Kozlowski would soon be indicted for looting the company, Tyco was on the verge of declaring bankruptcy, and the company's reputation was in tatters. True, Breen was being richly rewarded for his attempt to resuscitate Tyco: a $3.5 million signing bonus, a $1.5 million annual salary, and a bundle of stock options. But no one welcomes failure, especially the CEO of a high-profile company. Breen focused acutely on the task at hand: to pull Tyco out of its death spiral. And for that, he'd have to make a string of difficult decisions -- fast.

"I had this major corporation in crisis mode, and I didn't have a staff to answer the phones."

First, Breen had a whole lot of firing to do. Kozlowski's chief financial officer, Mark Swartz, was still working at the company. By September, Swartz had been persuaded to resign; Tyco later sued him to try to recover $134 million in what it felt was excessive pay, and federal prosecutors put Swartz on trial with Kozlowski earlier this year. (That case ended in a mistrial.) Breen also cleaned out Tyco's corporate staff. "I had this major corporation in crisis mode, and I didn't have a staff to answer the phones," Breen remembers. It was, he says, a $36 billion startup.

One of Breen's gutsiest moves was to replace the entire board of directors -- something that had never been done before at a company of Tyco's size. This was the board that had just hired him as CEO. Some corporate-governance experts were opposed to the idea, worried about the break in institutional continuity. But Breen was convinced that Tyco "needed a clean sweep to send a message to the market that this is going to be a different company."

The board was split; five members didn't want to resign, and several retained legal counsel. But eventually, Breen and the board hammered out a compromise that satisfied everyone. Two of the old directors would remain for a year as nonvoting advisory members to maintain continuity, but all the others agreed not to stand for reelection at the next annual meeting. "There's no way I could've backed down," he says. "If we didn't replace the board, we wouldn't have been able to proceed."

Of the 300 people who now work at the company's new, more modest headquarters just outside Princeton, New Jersey, fewer than a dozen were employed two years ago. In the field, two of Tyco's five division heads were also replaced. Did everyone need to go? Probably not, but Breen wasn't taking any chances. All told, the housecleaning represents one of the biggest management upheavals ever.