Sarah reels from a shocking discovery, and becomes desperate to find answers; after following a lead, Sarah finds herself in a harrowing encounter.
Sarah takes the day off to reconnect with Kira; Cosima infiltrates an exclusive Neolutionist fertility research center and makes a shocking discovery of their clandestine experiments.
Helena takes shelter behind enemy lines, and Sarah and Art struggle to protect her and end the siege.
Sarah and Rachel must come together for the greater good; Cosima and Susan disagree about the ethical implications of human experiments.
Alison's loyalty to the clones is questioned; Cosima makes a final attempt to discover a cure.