“You need to have more faith in me,” he said.

That evening he went over to a friend’s house. Near midnight, I called him. “This isn’t adding up,” I said. “You’re up past dawn. You’ve been spending money on restaurants. Other parents tell me you do nothing but gamble at their houses.”

He had shown me everything, he insisted. I reiterated my concern and my determination to get to the truth. We hung up. I lay awake. Around 4 a.m., I remembered hearing Dan and a friend debate the merits of PokerStars versus Full Tilt Poker. He could be playing, I realized, on another site. Somewhere, perhaps in his e-mail, I could find a Full Tilt account; I could call his bluff.

So there I was, the sun just rising, logging onto Full Tilt Poker in the guise of my son. I clicked the tab for “My Account.” The balance read $12,000. I clicked “Recent Activity.” He had been playing hundreds of games and tournaments, all summer long. I went to “Contact information” and changed the password and the e-mail address. I logged off, returned to Dan’s e-mail account, deleted the messages from Full Tilt and emptied the Deleted Items folder. My entire body shaking at this point, I went upstairs to tell Donald what I had done.

From the moment he could move puzzle pieces into place, Dan loved games. In preschool, entranced by Mario Bros. on Nintendo, he invented and acted out competitions with Mario and Luigi, whom he called “the Widgie.” When he couldn’t settle down for nap time in kindergarten, the computer teacher led him to the lab, where he spent the hour racking up magic coins. At home he discovered Monopoly; when everyone else was sick of the game, he played against his own imaginary opponent. At 6, when basketball grabbed his attention, he hung around the court across the street from our house and hustled free-throw competitions with older kids; if none showed up, he pretended to be Michael Jordan and Dennis Rodman and played one on one against himself. By fourth grade, he spoke in terms of “winning the test” at school.

By then, too, Dan had shown himself a gifted athlete and switched from basketball to tennis, where he could fight it out all by himself and take home the prize. Eventually he would garner a national ranking and player-of-the-year trophies. Although tennis distracted him from college preparation, the physical fitness and confidence it gave him assuaged — just barely — a mother’s worries.

Between tennis matches and on nontennis weekends, Dan and his friends played cards. They were part of a national craze set off by the televised World Series of Poker and its sudden elevation of poker players to media stars. Some parents worried about the $5 buy-in games of Texas Hold ’Em that were held in various basements, including mine. I countered that I was glad the boys were talking to one another rather than staring at a video screen; that those who lost would play Ping-Pong or foosball. I actually taught Dan his first casino game, blackjack. When he was learning arithmetic, we had a jar of pennies on the kitchen counter, and one day I asked Dan and his brother if they’d like to learn a game in which they counted to 21 — and if they won, they got to keep the other players’ pennies. In short order, Dan owned the whole jar.

The college Dan chose to attend, Old Dominion University in Virginia, wasn’t his first choice. While many schools wanted his tennis prowess and high SAT scores, they balked at his grades. Old Dominion, a commuter school in Norfolk with a crack tennis team, was willing to take him. To me, Dan seemed to be going to college for all the wrong reasons. There was nothing he wanted to learn. He wanted only to get away from home and to follow the same path that his tennis competitors were on. But when Dan would not consider a “gap year,” even at a prestigious tennis academy, I stipulated that he take out a private student loan in the amount of the scholarship that he could have received from Old Dominion had his grades been better. If he finished the year in good standing, I would repay the loan.