One of Us

Juliet arrives at the beach camp. With Jack. He trusts her. Nobody else does. Sayid confronts her immediately. "What do you know about us?" Juliet doesn't flinch.

Flashback. Juliet arrives on the island. Submarine. Mittelos Bioscience. Ben welcomes her. Her mission: understand why pregnant women die on the island. All of them. In the second trimester. Juliet fails. For three years. She wants to leave. Ben refuses. "Your sister has cancer. If you stay, I'll cure her." Blackmail.

On the beach, Claire falls ill. Juliet knows exactly what to do. She finds a medical kit hidden in the jungle. She saves Claire. The camp begins to accept her. But the final scene reveals the truth: Ben made Claire sick. Juliet knew. She's a mole. The plan works.