Contains spoilers for this episode and earlier episodes.
Cobel tells Mark that Cold Harbor is the last of a series of files that have produced new versions of Gemma. When this final innie completes its assigned task, Lumon plans to remove Gemma’s chip, which Cobel says will kill her. Mark’s outie, Devon and Cobel try to reach his innie through recorded messages. At Lumon, Mark finishes the file with Helly beside him, while Milchick and a marching band celebrate the completion.
Helly traps Milchick in a bathroom and Dylan barricades the door, giving Mark time to reach the testing floor. In the Cold Harbor room, Gemma’s innie must dismantle the crib Mark built for their baby. Mauer and Jame watch as she takes it apart without emotion. Lorne is set to sacrifice a goat nearby, but Drummond is distracted by Mark’s break-in. He attacks Mark; Lorne intervenes and subdues him.
Mark holds Drummond at bay with the cattle stunner and takes him into the elevator. As it switches Mark to his outie, he accidentally fires the device, killing Drummond. Mark uses Drummond’s blood to pass the biometric lock, frees Gemma, and reunites with her as their outie selves. On the way back up, the elevator switches them into their innies again. Mark guides Ms Casey to the exit stairwell, where she becomes Gemma, but he turns back toward Helly. He and Helly run through Lumon as Gemma calls after him.