Meanwhile, Dontember has made his way back to the lab at Formerly Harvard University and sadly no one is there to greet him. Not even a note! But he gets to work assembling his device, working with the holograph schematic, which might actually make this fun like putting together Lego! He's got those crazy red rocks, which he reduces to powder using a blowtorch (?) and then mixes with water or some other clear liquid, and -- look, eventually it's some sort of yellowish gel or something in a tube. Science!
The Fringe team arrives at a Resistance safe house, where they're introduced to field surgeon Tobin, who's going to be assisting them in preparing Olivia with the Cortexiphan. Walter's a little put out that they weren't able to acquire a defibrillator in time, but Tobin at least has some adrenalin, which Walter grudgingly says is risky but will have to suffice.
Olivia sits down and pulls open her shirt a little bit so Walter has access to the back of her neck -- because obviously to take effect quickly, the Cortexiphan needs to be injected directly into her brain stem. He sticks the first dose into the special pneumatic injection gun and fires it home, and we go a little Requiem for a Dream with dilated pupils and pumping heart. Olivia gasps and Astrid notes that her heart rate is elevated like YEAH I SHOULD THINK SO, and Walter gets the second dose ready and injects it. The effect is even more pronounced, and Olivia can't even focus on Peter. Tobin, who doesn't appear to be overly familiar with crazy Dr. Bishop, thinks this is all madness and says they're going to kill Olivia. Take it easy, Tobin. Dial it back a little. It's the series finale, so it's not like you're going to turn Tobin the Resistance Surgeon into a fan-favorite recurring character by dialing it up to eleven or anything. Walter grimly tells Peter to hold Olivia down, and shuts up Tobin: "I created Cortexiphan. There is no better authority."
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.