So that gives Olivia a little time to see right through Peter, as Walter pointed out, and guesses that Peter didn't really sell his dad's books for money: "Walter's got heaps of valuable stuff. Why did you just sell his books?" After a moment, Peter admits to not being "very fond" of him at the time, and the books were among his dad's favourite possessions. Peter does look quite regretful "And no, to answer your question, I'm not proud of it." I really hope Olivia didn't actually plan on asking: "Are you proud of it?"
Markham interrupts the confession by returning with the sales info: The books were bought last year by an Eric Franko, who lives over in Kendall Square: "He struck me as a real weirdo," says Markham, and Peter cracks, "Coming from you, that's saying something," and then decides "I owe you one" is a little more appropriate than insulting his friend.
We watch the Nazi listen to classical music while he tinkers away in a lab. Can't serial killers ever listen to pop music? Would it seem less creepy or more creepy if he were listening to Ke$ha right now? I say more. It looks like he's putting together Sterno cans, you know, those little cans that caterers put under warming dishes?
Meanwhile, Peter and Olivia are knocking on a door and getting no response. Olivia shines her flashlight in the dark window and says it doesn't look like anyone's there, so Peter is more than happy to pick the locks in the name of justice (and getting his dad off his back). Olivia draws her gun and they enter.
There is Nazi stuff everywhere, especially flags. It's like Von Ribbentrop's college dorm room. There are pictures of Hitler, some sort of huge Nazi collage on one wall -- not exactly a place it's easy to bring home a first date not named Eva Braun.
A dude comes in a side door, and Olivia swings her gun around and orders the guy to get on his knees. A moment later, we're looking very closely at the Nazi mosaic, which is made up of hundreds of pictures of puppies and kittens, and Franko explains that his art is about "the banality of evil," to borrow Hannah Arendt's phrase: "showing history's tyrants as these regular schmucks." Peter sarcastically calls it "deep," and doesn't point out that Franko is also wearing a T-shirt with a swastika on it. Sure hope everyone looks at that ironically! Peter asks where the German books Franko bought from Markham are.