A woman missing for seven years turns up at a hospital with strange scars on her back but can't -- or won't -- reveal where she's been.

The OA retraces the dramatic twists and turns in her life after a childhood accident, leading up to a fateful encounter far from home many years later.

An agonizing dilemma gives OA a new perspective on the group's plight. Homer resolves to find out what Hap's experiments are really about.

Karim returns to the house with reinforcements, OA tries to access Nina's memories, and Hap offers to discharge Scott -- after one last experiment.