S4 E4: Sarah realizes her goals have aligned with a former enemy and forms a precarious alliance in hopes of getting to the head of Neolution. Alison heads a mission to infiltrate a Neolutionist fertility clinic that Beth investigated, and sends Donnie and Felix in undercover. Back at the lab, Cosima and Scott receive a special delivery from Alison. As Rachel grows closer to Charlotte, Susan leaves a devastating decision in Rachel’s hands. A desperate Sarah returns to Dizzy needing his help again.