Plot summary
Paul discovers the hair samples from the women the Castor clones assaulted, and that Sarah is suffering from negative side effects after being given some of Rudy's blood. Alison makes significant money from the drug deals and plots with Jason to expand further by buying her mother's beauty shop Bubbles to be used as a front. In an attempt to find Sarah, Felix has Scott bring him to Rachel to learn her location but Rachel does not know. However, Scott realizes that Rachel was painting symbols from Ethan's notes. Cosima examines Gracie and learns that the Castors' defect is sexually transmitted and renders women infertile.
Paul has Coady arrested and takes charge of the base until reinforcements arrive. However, he later realizes that even his superior David Benchman is conspiring against him, as Coady is planning to weaponize the defect. Rudy is recalled from searching for Helena to help Coady. Paul helps Sarah, who has recovered, to escape, but he decides to stay behind. He kills a Castor clone, Miller, but is stabbed in the process. Paul urges Coady to stop. When she responds by shooting him, a dying Paul releases a grenade, destroying Abel's remains. Helena, who returned, finds Sarah on the way out.
Credits
Adapted from Wikipedia contributors, List of Orphan Black episodes. HTML formatting and reference markers removed.