Martin Silkwood has no idea anyone has him under surveillance when he steps onto the D.C. metro one Monday night. Why would they? He's no one special. Just a 40-year-old partner in a public accounting firm. But Martin has problems. Big problems. Three nights earlier, his wife left him, taking their two young kids and the dog with her. That was the last time he had heard from any of them. Their disappear-ance is what he's thinking about when a stranger bumps into him and warns him to "watch it!" Moments later, after knocking the wind out of Martin, the stranger draws near. He addresses Martin by name and tells him he already has "watched it," referring to the small DVD that he has just slipped into Martin's pants pocket."Now, it's your turn," he says. Then, he disappears out the door and into the crowd.