Plot summary
Art sneaks in, knocks out Engers and finds Helena. Coady finds them and forces Art to tend to Helena at gunpoint, but the two work together and Art disarms Coady while Helena finally kills her by jamming a screwdriver into her neck. Sarah battles and kills Westmorland/Mathieson by crushing his skull with his own oxygen tank, saying the sisters survived and evolved beyond him. Sarah and Art help Helena deliver two healthy twin boys. Months later, Helena is living with the babies in the Hendrix garage and the clones and their allies meet for Helena's baby shower.
With no conflict left to focus on, Sarah feels like the same failure of a mother and wants to run again. Her sisters calm her, so she happily stays. Rachel meets with Felix to give him the list of all 274 Ledas in the world. Though not part of the group and without her elitism anymore, Rachel is free. The sisters' journey ends as Alison and Donnie enjoy their happy marriage; Charlotte is taken in by Art; Helena names her babies after Arthur and Donnie; Cosima and Delphine travel the world curing all the unaware Ledas; and Sarah and Felix take Kira for a day at the beach.
Credits
Adapted from Wikipedia contributors, List of Orphan Black episodes. HTML formatting and reference markers removed.