Pamela Davis, blond suburban mother of three, was told that her bra would be the best place to wear the wire that kick-started a long investigation into Chicago graft and that ultimately caught the governor of Illinois trying to sell Barack Obama’s Senate seat. Davis is the president and C.E.O. of Edward Hospital, in Naperville, Illinois. She is proud of the fact that on her twenty-year watch the hospital has grown from a hundred-and-sixty-two-bed community facility to a four-hundred-and-twenty-seven-bed regional medical center that leads the county in babies delivered.

Back in 2003, Davis was trying to get approval for a new medical office building from the Illinois Health Facilities Planning Board. A night or two before a hearing was to be held, Davis recalled, something strange happened. A business acquaintance of hers, Nicholas Hurtgen, then a managing director of the Chicago office of Bear Stearns, called her at home and told her that unless she agreed to use a certain contractor she should pull her building request, because it wasn’t going to be approved.

She ignored the warning and went off to the board hearing, where she was surprised to find that her request was denied. “I was humiliated,” she said. “They were mean. So I walk off, and then a different guy comes up to me and he says, ‘We told you to pull your project. Call me.’ And right then I decided to call the F.B.I.”

At first, the agents she contacted thought she was a crank. “I could tell they were laughing at me. Most people who call the F.B.I. are crazies. So they sort of humored me and said, ‘O.K., we will come out and listen once.’ ”

A few days later, three F.B.I. agents met her at her office, bugged her phone, and outfitted her with the wire to put in her bra. Then they set up camp in a van in the parking garage and waited. “They said, ‘You tell nobody anything, not even your husband.’ They were laughing at me and I was laughing at them.”

The agents had instructed Davis to invite Hurtgen and Jacob Kiferbaum, the contractor whom he had mentioned over the phone, to meet at her office. When they arrived, the F.B.I. men listened in on the conversation from the van.

As Davis recalled, “They say, ‘We told you to pull the project.’ And I say, ‘Yeah, why do I need you?’ And they start saying, ‘If you don’t hire us, you will never get this project approved.’ After about five minutes, my phone rings, and now the three F.B.I. guys in the parking garage are saying, ‘It’s extortion! It’s extortion!’ They yell, ‘Get ’em out! Get ’em out!’ So I hang up the phone.

“Now everybody is looking at me. These guys have driven two hours to have a meeting with me. And I say to them, ‘I am so sorry, I have a family emergency.’ I’m making this up as I go along. After that, I had the three stooges in the garage telling me they’d help me.”

That episode helped start United States Attorney Patrick Fitzgerald’s Operation Board Games. For the next seven months, Pamela Davis, hospital administrator, became Pamela Davis, secret agent, helping to expose a multimillion-dollar scam that at times resembled a spinoff of “The Sopranos,” guest-starring the back office from “Grey’s Anatomy.” Davis attended long lunches and boozy dinners with crooked businessmen, listening (and taping) as they talked of grafting off the hospital industry. She would slip the tapes to her F.B.I. handlers at Marshall Field’s makeup counters in malls around suburban Chicago.

Davis taped all sorts of incriminating conversations, but she never quite got used to spycraft. “The wire is a little tiny square thing I put inside my bra. I thought it would fall out all the time,” she said. “Oh, the logistics of getting this stuff done! One morning, I had to meet one of the F.B.I. guys in my office at 6 A.M. so he could hook up a wire to tap my phone. He was under my desk, on the floor. It looks kinky! My administrative assistant pops her head in, and there’s this man under my desk, and she says, ‘Oh, my goodness,’ and leaves. And I go, ‘What am I supposed to tell her?’ He says, ‘I don’t know. That never happened to me before.’ ”

Eventually, the “bad guys,” as Davis calls them, told her she could build her new building if she agreed to add several million dollars to the deal for Kiferbaum. “The F.B.I. said, ‘Sign it—it makes the case better.’ But I couldn’t do that. How could I possibly sign something like that and cost my organization money? I didn’t know what the hell to do.” (The F.B.I. was unable to comment.)

Davis got a court order allowing her to hire a lawyer and to tell her hospital-board chairman what she was up to. After seven months, the Chicago Sun-Times published her name in a blind item about an ongoing corruption investigation, and Davis’s role in the case was over. Her tapes of Stuart Levine, a corrupt health-board member, helped lead to his becoming a federal witness in the trial of Antoin (Tony) Rezko. (Kiferbaum pleaded guilty to attempted extortion in 2005. Hurtgen maintains his innocence, and his lawyer disputed Davis’s account.)

As Fitzgerald’s probe widened, more wiretaps were put in place, and more corruption was exposed. Eventually, the governor of Illinois was recorded discussing the sale of Obama’s Senate seat. Davis, who describes herself as a political independent, says she’s disgusted with politics now, although she did vote for Obama. And she still hasn’t received state approval for her hospital expansion. ♦