"Fourth Gen. Delayed fuse. Blast radius of one hundred metres. And once it's armed, it can't be deactivated, so when you use it, make sure you don't stick around." Well, like Chekhov always said, if you introduce an anti-matter bomb in the fourth act, it must go off in the fifth.
Olivia asks how he got all this stuff, and Broyles says it wasn't simple. Well, that explains that! "Seeing you makes me realize how much I miss Boston," Broyles tells Olivia, adding that maybe he'll put in for a transfer.
Just then, they notice an Observer standing nearby. Everyone freezes, then Broyles tries a nonchalant wave and "It's all right! I've apprehended them!" It's a terrible cover, but I don't think it was intended to do anything other than buy Broyles enough time to pull his gun and plug the guy. "They found you," Broyles tells them, and it's Olivia who spots the tracker with the blinking red light -- you know, like trackers tend to have -- on the underside of the car.
So the concern is immediately twofold -- protecting Broyles' cover and protecting the plan. Broyles tells them they won't make it by car, but they should run. Instead of taking the tracker off and escaping in the car? Another Observer appears, knocking Peter off his feet with a pulse weapon before Etta shoots him, and then the gang gets the hell out of there, heading for some nearby warehouses as Broyles leaves tracks in his car. Just after everyone makes it out of sight, a couple more Observers pop into view. They stand there, facing the buildings, and one of them silently lifts his arm and points towards them.
After the commercial break, the team is hobbling its way through a warehouse, while all around Observers and Loyalists are swarming the area, including Captain Windmark, striding cinematically into a darkened structure. "There," he says, after he and the other two hit their marks, and they continue on. What, is he a bloodhound?
The Fringe team hears the sirens and shouting and know that their enemies know they're there, but there's only so much running you can do when Observers can literally pop out of thin air in front of you and start shooting. Peter and Olivia get separated from Walter and Etta by some bullet-spewing Loyalists, so Peter and Olivia keep pushing forward to get out, Peter assuring Olivia they'll double-back to get Walter and Etta (if Walter survives this, he might want to think about learning to shoot a gun).