Season: 3
Episode: 16
Title: One of Us
Flashback: Juliet
Synopsis:
Jack's joyous reunion with his fellow survivors is cut short when they realize that accompanying him is one of "The Others." Guest starring are Robin Weigert as Rachel, William Mapother as Ethan Rom, Brett Cullen as Goodwin, Andrew Divoff as Mikhail, Nestor Carbonell as Richard Alpert, Joah Buley as other dude and Tyrone Howard as airport guard.
SPOILERS
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