They go for a walk (roll) and Olivia explains about the damage to the building, but they think the underground structure is intact. Walter says he was hoping she's got access to technology that could change the atomic structure of the rubble and help them clear it. "The Observers created a device that dramatically alters atmospheric pressure, speeding up molecules in all the matter in a controlled area. A process called sublimation," says Nina. As Walter knows, "sublimation" is the term for the conversion of a solid directly into gas, and Nina explains that they used the technology to clear large areas of land for construction, like when they were prepping Central Park to build their air-degradation device. She tells them she'll meet them at the south side of the building in ten minutes.
Moments later, the Fringers bring the van around, and Nina rolls up to greet Walter when he gets out of the van. She asks if he's angry at her, and he asks why he should be. "Because I told Etta and Simon how to re-implant the portion of your brain you had removed," she says. Walter, looking like he is pissed about that, says she did what was necessary, and Nina agrees with that, explaining they needed his intellect restored. "There was a lot at stake. There still is," she says, and then asks if he has noticed any changes in his personality since the implant. This draws Walter up short, and he admits to "some," and Nina says the tissues are integrating faster than she thought they would. "The man I was before, do you see him in me now?" Walter asks her. Nina says she doesn't, but Walter would know better than she does anyway. Especially since she's talked to him all of FORTY-FIVE SECONDS here. She asks if he's worried. He shakes his head slightly.
"The man I was before, he was consumed by ambition, by hubris. He never cared about anyone. All he cared about was walking with the gods," he says. This time, explains Walter, he's got Peter, who won't let him become that man again. Poor Walter doesn't know Peter's got his own shit going on.