Broyles says they could buy some time by pumping fentanyl gas into the building: "Knock them out long enough to synthesize a cure. We could have a gas truck here in ten minutes." McFadden's not having it though, because the gas won't disperse, what with the building's ventilation system being down, and he's not going to risk sending any of his people inside to turn it on. Olivia immediately volunteers, and after Broyles agrees, McFadden gives them fifteen minutes.
After the commercial break, Olivia's running through the building with a map, and gets to an elevator bank. At the same time, Peter is racing back to the security desk at the front entrance for some reason, but he happens to spot Olivia entering an elevator on the security camera. Broyles radios her to tell her the gas truck is there, and he wants to know what her "twenty" is, and she tells him she's on her way to the parking garage. Peter studies the monitor, looking to figure out where she's going, while Olivia checks her map because SHE doesn't even really know where she's going.
She pushes through a swinging door into the parking garage and is immediately attacked by Peter. Stunned, she pulls her gun and tries telling him that she's there to help him. No, not by giving him her gun, as he requests. She warns him that the army is going to shoot him: "They're gonna kill us all anyway. The cure is out there. They're lying to us. And you locked me in here," he says, stomping forward. Naturally, Olivia can't actually shoot Peter, and they struggle, Peter slamming her on the trunk of a car. "You betrayed me!" he roars as they fight. Peter slams her against a wall, banging her gun. The gun goes off, and Olivia drops it and it skitters under a car. Olivia knees him in the groin and breaks free, diving across the floor to reach for her gun, but Peter stomps on her arm and grabs it first. He tells her to stay down, and points the gun at her, and then he wanders off.
Outside, Broyles is trying to get a hold of her, but she's not responding to the radio. So he calls Astrid, who tells him the ventilation system isn't on yet.
McFadden comes up to point out that the fifteen minutes are up, and Broyles asks for another ten minutes: "There are people in there that are like family to me." Wow, Broyles glowers at his family a lot. McFadden says, "I'm sorry," and walks away.
These things are happening all at once: Peter's in the elevator, loading a fresh cartridge into his gun; armed teams are entering the building through emergency exit; Olivia runs down the stairs to the building operations room, where she easily finds the control panel with its clearly labelled breakers and turns the ventilation system back on.