Things are going well with Michael and Donna, which is a sign that they're about to blow up. Sure enough, some of the employees plant the idea in his head that she's cheating on him. Against the more reasonable advice of Pam and Jim, Michael hires a private detective -- okay, it's Dwight -- to find the truth, but all that does is piss her off. Not badly enough for her to dump Michael, though, and in fact they start planning a trip together. But then Pam finds photographic evidence that Michael's not the only man in Donna's life. Michael confronts Donna, and she confesses the truth: she's married. Ouch.
In other news, Andy learns that the Sabre printers he's been selling might be prone to catching fire. Darryl sees a chance to repay a two-year-old grudge and tricks Andy into thinking he's in danger, as a whistleblower whom the company wants dead. But when Darryl springs the trap (tricking Andy into making an embarrassing video), it gets real. Let's hope Darryl learned his lesson: make a plan next time.
The clicking of Pam's mouse and Jim's pen is making Dwight crazy, but not for the reason you think: he thinks they're talking about him in Morse code, which of course he understands. Jim mocks, "Yep, that's what we're doing. In our very limited free time, and with our very limited budget, we went and got a nanny and then we went out and took a class on a very outmoded and unnecessary form of communication just so we could talk about you in front of you." And then he talking-heads, with Pam at his side, "Yep, that's exactly what we did." But what part of "outmoded and unnecessary" made them think Dwight wouldn't be a step ahead of them? Pam says this is their response to her asking Dwight to quit tapping his foot and his responding, "I will when you lose the baby weight." Back in the bullpen, Dwight apologizes to the Halperts. But various forms of clicking continue until Dwight gets up running for Michael's office: "Detonator? Where?" Michael's annoyed at the interruption, so Dwight puts on noise-cancelling headphones. Now he and Pam are angrily blinking at each other in Morse. Jim joins in, ending with a wink to us. It's true; you fight a war long enough, you become the enemy.
Michael THs about how well things are going with Donna. There's a clip of the two of them making out by Security while Hank watches over his breakfast and Angela walks by in disgust, so at least now everyone knows he's not making it up. He admits that he's having trouble focusing on his job. And to demonstrate this, we see him asking everyone in the staff meeting to brainstorm ideas for his upcoming weekend with Donna. The subject of their recent drive to the Poconos comes up, and Kelly asks, "Are you sure she's not cheating?" The reason she asks is because Ryan took her so some out-of-the-way diner when he had two girlfriends. "It's in a Life magazine spread about Americana!" Ryan protests heatedly. Notice he doesn't deny having had two girlfriends. Knowing this topic can never lead anywhere good, Pam tries to nip this speculation in the bud, and Michael's about to end the meeting. But then he remembers Donna won't say "I love you" after nine dates, when he said it on the second. "That seems quick, even for lesbians," says Oscar, which doesn't make it any less of a stereotype. Ryan rattles off a whole litany of cheating signs (which could also be completely innocuous) that he seems to know quite well. Pam is heroically trying to talk Michael down, but he says he can't stop his imagination: "I live in a fantasy world!" His moments of self-awareness are getting more frequent.