Seven years after vanishing from her home, a young woman returns with mysterious new abilities and recruits five strangers for a secret mission.

After waking up to a new life in San Francisco, OA is drawn into a search for a missing teen and begins to encounter familiar faces from her past.

While private eye Karim Washington scours San Francisco for a missing teen who was involved in a cryptic game, OA wakes up in unfamiliar surroundings.

At the clinic, OA discovers what happened to her friends back at Hap's. Karim turns his attention to a doctor who worked for Pierre Ruskin.

In Michigan, Steve begs the gang to try jumping to another dimension, and a presence in Buck's mirror inspires an unlikely pilgrimage.

Karim visits Nina at the clinic for help finding the secret entrance to the house. Meanwhile, Hap meets a fellow traveler, and Homer goes on a date.

After a harrowing ordeal, OA and Karim find themselves locked inside a labyrinth of puzzles. Nagging doubts prompt Homer to snoop on Dr. Percy.

As BBA and the kids head west, an alarming news report forces them to speed up their plans. Jesse wrestles with lingering trauma from the shooting.

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

While BBA and the others converge on the clinic, Nina persuades Hap to show her his research, and Karim unlocks one of the house's final secrets.