Series 2, Episode 7
The series shifts backwards into revealing the survival of the rear-end passengers who ended up on the island. Led by ex-cop-turned psycho Ana-Lucia, the small group on the other side of the mysterious island find their numbers getting smaller when some of them are taken under the cover of darkness. A bit of detective work on the part of one of them discovers that there is an infiltrator among them who is working for 'The Others'.
Interesting episode which is both frustrating and exciting at the same time. It helps define the other (newer) characters and bring them into the mix of the show. Most of the cast credited in the opening sequence do not actually appear in this episode.