"I'd see Mel crying, and I knew something was wrong, but she wouldn't talk about it," Darrell says.
At the Christmas party, Mel remembers being shaken when she saw the woman walk in with her sister-in-law.
"I turned to him and said, 'She brought that girl here because of you.' "
A week later, the woman called Darrell at work. They began a phone relationship in which Darrell would talk about his emotions, his dreams, his problems at home. And one day, he says, he decided to make this connection physical.
"I made this plan to go to [the woman's] house, but then I hung up the phone," he says, grappling with the memory. "You go through this whole thing of, 'I can't do this -- it's wrong. But I bet it would be fun.' "
All afternoon, he says, he vacillated between guilt and desire. Mostly guilt. At the last moment, he changed his mind. He wanted sex, but he loved his wife. It turned out that Mel knew something was wrong -- when she confronted Darrell, he recalls, it was a relief. He confessed all of his feelings for the other woman.
"It totally crushed everything," he says. "Nothing I said mattered. Every time I left the house I knew what she was thinking."
Today, four years after Darrell did not have sex with another woman, Mel still looks devastated when they talk about it. When asked if she trusts her husband, she hesitates.
"Almost," she says.
* * *
This sort of lasting pain, and the sense of betrayal that accompanies it, is a particularly American response.
"This outsize preoccupation with monogamy doesn't seem to do Americans much good," Druckerman writes. And "when Americans do cheat, it gets very messy. Despite the existence of our vast marriage-industrial complex, adultery crises in America last longer, cost more, and seem to inflict more emotional torture than they do in anyplace else."
The language that accompanies modern-day infidelity in the United States points to this trauma -- it tends to involve loaded words such as "betrayed spouse" and "D-Day," to describe the day a spouse discovers his or her partner's affair.
This raw language is in full, sometimes graphic, display at www.SurvivingInfidelity.com, one of the busiest infidelity support sites on the Internet. It has more than 27,000 registered members, 200,000 page views a day, and about 6,000 new posts daily in forums such as "Just Found Out," "Reconciliation," and "Divorce/Separation."
The creators of the site are a husband and wife in Texas who went through their own infidelity trauma a decade ago. They asked that they only be identified by the initials they use online, M.H. and D.S. Their story shows another aspect of modern-day American infidelity -- the Internet.
D.S., the wife, was the one who cheated. Her affairs started in a chat room, only a year after she had married the friendly Web development co-worker who had won her heart. She started communicating online with other men, and soon the chats became sexual. E-mails turned into dates, which evolved into sex.
Although there is debate about the numbers, some researchers hypothesize that the Internet's ability to provide both pornography and clandestine access to other partners has helped raise the adultery rate among young couples in America. University of Washington researchers found that in 2006, about 20 percent of men and 15 percent of women under 35 said they had been unfaithful -- up from 15 percent and 12 percent who said so in 1991.