Third dose goes in. Olivia appears to be dying. Peter pleads no más and Astrid wants to stop, but Walter quietly says she needs all four doses because she's going to be crossing over four times. "Do you want to leave her stranded on the other side?" he asks. You know what? Things seem nicer over there. Maybe Peter wants her to stay over there. But he pulls his hand from the back of Olivia's head and Walter injects the final dose. Olivia screams and collapses into Peter's arms. But, you know, not in the good way.
After the commercial break, the Observer scientists are staring at Michael's brain scan in confusion, noting the uncharacteristic development in the brain's emotional centers. The abnormally enlarged limbic system has "sent tendrils" into the brain's cognitive centre and integrated intellectual and emotional activity to an extent heretofore thought impossible. While you're in there, can you see why he's not talking? One of the Observers says he'll make the report.
Back at the safehouse, Olivia rests and Peter watches her. Walter tells him "Sacrifice is hard" and then perhaps remembering that Etta RECENTLY DIED adds that Peter's no stranger to that. Neither are you, Peter reminds him. Walter, looking like he's getting emotional, says, "Peter -- " as though he's about to tell his son something, but when Peter prompts him to continue, Walter appears to think better of it and says, "You're very strong, son."