Maybe the FBI's response wasn't as impressive as I thought it was going to be, as all I see are Olivia and Charley hunting high and low. Grant gets a call telling him to head for the Dewey Square exit, and Peter passes that on to Olivia too.
Olivia spots Grant at the exit, but before she can get to him, he's subtly bumped by Buddy from the bus. A second or two too late, Olivia orders Grant to turn around with his hands up. He turns around, but his hands are clutching his chest, which is bloody. Grant collapses. Worse luck: he doesn't have the briefcase, but it doesn't take too long to find it, because obvious metal exchange briefcases never take too long to find, and Olivia and Charlie manage to corner the guy. Well, perhaps not "corner," exactly, given that they leave him room to very deliberately step in front of a bus passing by.
So what was it all for? People in white coats in labs that look as advanced as anything you might see in a toothbrush commercial open the briefcase, which contains foam cut perfectly to accommodate a small slide-open case in which is a translucent yellowish plastic disc. Grant really went to a lot of effort to wrap the thing up all pretty, didn't he?
Later, Broyles shows it to Olivia and says they don't know what it is, but they're hoping the guys at NSA might have some ideas. "So eleven innocent people died today, we risked losing another by drilling through his head, all for something we know nothing about?"
Broyles asks if she ever smiles, and points out they ID'd the shooter, whose fingerprints link him to two other Pattern cases. "Not only can we put a face to these people, but we know they're communicating, and how. I'd say that's an impressive day's work." Yeah, seems like a fair trade for eleven lives, Broyles.
And I guess she's earned some trust, because he says there were three models in Roy's apartment that have to do with things that haven't happened yet, and he wants Olivia to have a look. Olivia looks absolutely thrilled, but he didn't say anything about overtime pay. Like she hasn't had a long enough day already.
Later, everyone's still hanging out in the Harvard lab when Olivia comes in, like don't you people have ANYWHERE to go? Roy's not hearing voices anymore, and they figure that when the FBI showed up at South Station the Pattern folks knew the ghost network was compromised and have stopped broadcasting on it anymore. Peter, sitting at the piano says, "Any requests?" and Olivia says "Bach," which Peter says is "too stuffy" and then he starts playing "Someone To Watch Over Me," like WHY DID YOU BOTHER ASKING FOR REQUESTS anyway?