When Jack's health is seriously compromised, Kate and Juliet must learn to work together in order to save him; and something goes wrong as Sawyer, Claire, Aaron and Miles continue their trek away from Locke's camp and back to the beach. Guest starring are Ken Leung as Miles, Jeremy Davies as Daniel Faraday, Rebecca Mader as Charlotte, Jeff Fahey as Frank Lapidus, Sam Anderson as Bernard, L. Scott Caldwell as Rose and Kevin Durand as Keamy.* Kate and Juliet perform an emergency appendectomy. Jack just can’t stop making Kate perform surgical procedures! Is the island trying to kill Jack? Will Kate count to five? * Lapidus returns to the island and runs into Sawyer’s group. Will we learn that Lapidus is on the freighter and the island simultaneously? Will he have a conversation with himself? * More flashforwards, again showing Jack’s life away from Dharma Island. * Jack looks likely to pay an old friend another visit at the Santa Rosa Mental Institute. * Though ABC doesn’t mention him in the episode’s synopsis, John Terry may again turn up as a not-dead Dr. Christian Shephard. After tonight, four more season-four hours to air. 10 p.m. Thursday. ABC.